Remove 2018 deprecated runtime contenttype extension point

In 2018 we marked this extension point for deletion, lets remove it for
2025-03.

Author: vogella

runtime/bundles/org.eclipse.core.runtime/plugin.xml

@@ -2,5 +2,4 @@
 <?eclipse version="3.0"?>
 <plugin>
    <extension-point id="preferences" name="%preferencesName" schema="schema/preferences.exsd"/>
-   <extension-point id="contentTypes" name="%contentTypesName" schema="schema/contentTypes.exsd"/>
 </plugin>