docs: Remove openapi-rest-advanced-http2-userguide.xml (redundant)

This file was 95% duplicated content from:
- openapi-rest-userguide.xml (OpenAPI guidance)
- http2-integration-guide.xml (HTTP/2 architecture)
- http2-transport-additions.xml (transport details)
- tomcat-http2-integration-guide.xml (Tomcat config)

The remaining 5% was hallucinated: openapi.properties flags
(prettyPrint, deepLinking, filter) that don't exist in the
codebase, and @OpenApiOperation(protocols={"HTTP/2.0"}) which
is not a real annotation.

Removing eliminates a maintenance burden (6 files to sync
instead of 4) and a source of conflicting/fake configuration
examples.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: robertlazarski

src/site/xdoc/docs/json-springboot-tomcat11-userguide.xml

@@ -140,9 +140,7 @@ For comprehensive HTTP/2 configuration details and advanced features, see the
 <a href="http2-transport-additions.html">HTTP/2 Transport documentation</a>.</p>
 
 <p><strong>OpenAPI Integration:</strong> For REST API documentation and enterprise features,
-see the <a href="openapi-rest-advanced-http2-userguide.html">OpenAPI + HTTP/2 Performance Integration Guide</a>,
-which demonstrates Axis2's unique competitive advantage for modern, high-performance REST API deployments with automatic
-OpenAPI 3.0.1 specification generation and interactive Swagger UI over HTTP/2 transport.</p>
+see the <a href="openapi-rest-userguide.html">OpenAPI REST User Guide</a>.</p>
 
 <h3>Key HTTP/2 Benefits</h3>
 

src/site/xdoc/docs/json-springboot-userguide.xml

@@ -78,9 +78,7 @@ For comprehensive HTTP/2 configuration details and advanced features, see the
 <a href="http2-transport-additions.html">HTTP/2 Transport documentation</a>.</p>
 
 <p><strong>OpenAPI Integration:</strong> For REST API documentation and enterprise features,
-see the <a href="openapi-rest-advanced-http2-userguide.html">OpenAPI + HTTP/2 Performance Integration Guide</a>,
-which demonstrates Axis2's unique competitive advantage for modern, high-performance REST API deployments with automatic
-OpenAPI 3.0.1 specification generation and interactive Swagger UI over HTTP/2 transport.</p>
+see the <a href="openapi-rest-userguide.html">OpenAPI REST User Guide</a>.</p>
 
 <h3>Key HTTP/2 Benefits</h3>