Remove Maven prerequisite

Fixes
```
[WARNING] The project
org.eclipse.platform:eclipse.platform.releng.buildtools:pom:1.1.0-SNAPSHOT
uses prerequisites which is only intended for maven-plugin projects but
not for non maven-plugin projects. For such purposes you should use the
maven-enforcer-plugin. See
https://maven.apache.org/enforcer/enforcer-rules/requireMavenVersion.html
```

pom.xml

@@ -18,9 +18,6 @@
   <artifactId>eclipse.platform.releng.buildtools</artifactId>
   <version>1.1.0-SNAPSHOT</version>
   <packaging>pom</packaging>
-  <prerequisites>
-    <maven>3.9.0</maven>
-  </prerequisites>
 
   <properties>
     <tycho.version>4.0.6</tycho.version>