Limit the visibility of "Find References" to the active Generic Editor

The visibility of this menu item must be restricted because other
editors like the Xtext Editor come with their own "Find References"
action.

Fixes https://bugs.eclipse.org/bugs/show_bug.cgi?id=564610

Author: oleosterhagen

bundles/org.eclipse.ui.genericeditor/META-INF/MANIFEST.MF

@@ -2,7 +2,7 @@ Manifest-Version: 1.0
 Bundle-ManifestVersion: 2
 Bundle-Name: %Bundle-Name
 Bundle-SymbolicName: org.eclipse.ui.genericeditor;singleton:=true
-Bundle-Version: 1.3.100.qualifier
+Bundle-Version: 1.3.200.qualifier
 Bundle-Vendor: %Bundle-Vendor
 Bundle-RequiredExecutionEnvironment: JavaSE-17
 Require-Bundle: org.eclipse.ui.workbench.texteditor;bundle-version="3.10.0",

bundles/org.eclipse.ui.genericeditor/plugin.xml

@@ -112,6 +112,11 @@
          <command
                commandId="org.eclipse.ui.genericeditor.findReferences"
                style="push">
+            <visibleWhen>
+               <reference
+                     definitionId="org.eclipse.ui.genericeditor.GenericEditor.active">
+               </reference>
+            </visibleWhen>
          </command>
       </menuContribution>
       <menuContribution