[RHIDP-12900]: Remove unused troubleshooting-rhdh-plugins title and fix broken xrefs (#1959)

Delete titles/extend_troubleshooting-rhdh-plugins/ (unpublished in Pantheon 1.9).
The shared module proc-troubleshoot-a-pod-startup-failure-after-enabling-a-plugin.adoc
is preserved (also included by extend_installing-and-viewing-plugins-in-rhdh).

Fix 2 broken xrefs referencing the old title-plugins-rhdh-about context,
remove orphaned introduction-to-plugins-book-link/title attributes, and
update 2 files that referenced them.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: themr0c

artifacts/attributes.adoc

@@ -160,8 +160,6 @@
 :installing-rhdh-orch-on-ocp-book-title: Installing RHDH with the Orchestrator Plugin on {ocp-short} using the {product} Operator
 :integrating-with-github-book-link: {product-docs-link}/html-single/integrating_red_hat_developer_hub_with_github/index
 :integrating-with-github-book-title: Integrating {product} with GitHub
-:introduction-to-plugins-book-link: {product-docs-link}/html-single/introduction_to_plugins/index
-:introduction-to-plugins-book-title: Introduction to plugins
 :learning-path-data-json-link: link:https://raw.githubusercontent.com/redhat-developer/rhdh/release-{product-version}/packages/app/public/learning-paths/data.json
 :manage-and-consume-techdocs-link: https://docs.redhat.com/en/documentation/red_hat_developer_hub/1.8/html-single/manage_and_consume_technical_documentation_within_red_hat_developer_hub/index
 :manage-and-consume-techdocs-title: Manage and consume technical documentation within {product}

assemblies/get-started_navigate-rhdh-on-your-first-day/assembly-integrate-and-customize-your-daily-tools-using-extensions.adoc

@@ -17,7 +17,7 @@ include::../modules/get-started_navigate-rhdh-on-your-first-day/proc-identify-in
 
 [role="_additional-resources"]
 == Additional resources
-* {introduction-to-plugins-book-link}[{introduction-to-plugins-book-title}]
+* {installing-and-viewing-plugins-book-link}[{installing-and-viewing-plugins-book-title}]
 
 ifdef::parent-context[:context: {parent-context}]
 ifndef::parent-context[:!context:]

modules/discover_about-rhdh/con-understanding-internal-developer-platforms.adoc

@@ -64,6 +64,6 @@ Support growing teams and applications while maintaining access to the same tool
 * {customizing-book-link}#configuring-templates[Configuring templates]
 * {techdocs-book-link}[{techdocs-book-title}]
 * {customizing-book-link}#proc-customize-rhdh-learning-paths_configuring-templates[Customizing the Learning Paths in {product}]
-* {introduction-to-plugins-book-link}[{introduction-to-plugins-book-title}]
+* {installing-and-viewing-plugins-book-link}[{installing-and-viewing-plugins-book-title}]
 * xref:integrations-in-rhdh_{context}[Integrations in {product}]
 * {authentication-book-link}[{authentication-book-title}]

modules/shared/proc-install-and-configure-an-external-techdocs-add-on-using-the-helm-chart.adoc

@@ -12,7 +12,7 @@ Preinstalled add-ons, such as `ReportIssue`, are included in the default `backst
 * The TechDocs plugin is installed and enabled.
 
 .Procedure
-. In your Helm chart, add the `global.dynamic` parameters required to install a dynamic plugin, as shown in {installing-and-viewing-plugins-book-link}#con-install-dynamic-plugin-helm_rhdh-installing-rhdh-plugins[Installing dynamic plugins using the Helm chart ]
+. In your Helm chart, add the `global.dynamic` parameters required to install a dynamic plugin, as shown in {installing-and-viewing-plugins-book-link}#installing-dynamic-plugins-using-the-helm-chart_install-dynamic-plugins-in-rhdh[Installing dynamic plugins using the Helm chart]
 +
 [NOTE]
 ====

modules/shared/proc-install-and-configure.adoc

@@ -31,7 +31,7 @@ This reinstallation is required due to the following fundamental architectural c
 
 * You are logged in to your {ocp-short} account.
 * You have an {product-very-short} instance installed using either the Operator or the Helm chart.
-* You have created a {installing-and-viewing-plugins-book-link}#rhdh-installing-rhdh-plugins_title-plugins-rhdh-about[custom dynamic plugins ConfigMap].
+* You have created a {installing-and-viewing-plugins-book-link}#install-dynamic-plugins-in-rhdh_installing-and-viewing-plugins-in-rhdh[custom dynamic plugins ConfigMap].
 * You have administrative access to the {product-very-short} configuration files.
 
 .Procedure