DOC-3021: Flatten duplicated nav nodes for Enhanced Media Embed and Export to PDF

Use the plugin page as the parent navigation node for Enhanced Media
Embed and Export to PDF, matching Export to Word and Import from Word,
so the plugin no longer appears twice in the navigation tree.

Author: kemister85

modules/ROOT/nav.adoc

@@ -298,18 +298,16 @@
 **** xref:revisionhistory.adoc[Revision History]
 **** xref:suggestededits.adoc[Suggested Edits]
 *** Content Conversion & Embedding
-**** Enhanced Media Embed
-***** xref:introduction-to-mediaembed.adoc[Enhanced Media Embed]
+**** xref:introduction-to-mediaembed.adoc[Enhanced Media Embed]
 ***** xref:mediaembed-server-config.adoc[Configure Enhanced Media Embed Server]
 ***** xref:mediaembed-server-integration.adoc[Integrate Enhanced Media Embed Server]
-**** Export to PDF
-***** xref:exportpdf.adoc[Export to PDF]
-****** xref:html-to-pdf-converter-api-v2.adoc[HTML to PDF Converter API]
-****** JWT Authentication
-******* xref:export-to-pdf-v2-with-jwt-authentication-nodejs.adoc[Node.js (8.4.0+)]
-******* xref:export-to-pdf-v2-with-jwt-authentication-php.adoc[PHP (8.4.0+)]
-******* xref:export-to-pdf-with-jwt-authentication-nodejs.adoc[Node.js (pre-8.4.0)]
-******* xref:export-to-pdf-with-jwt-authentication-php.adoc[PHP (pre-8.4.0)]
+**** xref:exportpdf.adoc[Export to PDF]
+***** xref:html-to-pdf-converter-api-v2.adoc[HTML to PDF Converter API]
+***** JWT Authentication
+****** xref:export-to-pdf-v2-with-jwt-authentication-nodejs.adoc[Node.js (8.4.0+)]
+****** xref:export-to-pdf-v2-with-jwt-authentication-php.adoc[PHP (8.4.0+)]
+****** xref:export-to-pdf-with-jwt-authentication-nodejs.adoc[Node.js (pre-8.4.0)]
+****** xref:export-to-pdf-with-jwt-authentication-php.adoc[PHP (pre-8.4.0)]
 **** xref:exportword.adoc[Export to Word]
 ***** xref:html-to-docx-converter-api.adoc[HTML to DOCX Converter API]
 ***** JWT Authentication