chore(config): retire orphaned issue templates from operator repos

normal-issue.md and new_version.md predate templating and were superseded by
the managed 01-normal-issue.md / 02-bug_report.yml set. They still sit in 15 of
16 operator repos (opensearch-operator is already clean). kafka-operator and
superset-operator also carry an old unprefixed bug_report.yml next to the
managed 02-bug_report.yml.

Adding them to retired_files so the next rollout deletes them fleet-wide.
state: absent is idempotent, so listing a file that is missing in a given repo
is a no-op.

Author: lfrancke

config/retired_files.yaml

@@ -6,3 +6,6 @@ retired_files:
   - .readme/static/borrowed/sdp_overview.png
   - .github/workflows/pr_pre-commit.yaml
   - .github/workflows/build.yml
+  - .github/ISSUE_TEMPLATE/normal-issue.md
+  - .github/ISSUE_TEMPLATE/new_version.md
+  - .github/ISSUE_TEMPLATE/bug_report.yml