fix: remove org.eclipse.xtend from test project required bundles

The test project created by PluginTestProjectManager listed
org.eclipse.xtend as a required bundle. After migrating away from the
Xpand library, this bundle is no longer in the test runtime, causing
PDE to produce an unresolved bundle error marker — the 5th marker that
made CheckQuickfixTest.testBulkApplyingQuickfix fail consistently
with expected:<4> but was:<5>.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: joaodinissf

com.avaloq.tools.ddk.xtext.test.core/src/com/avaloq/tools/ddk/xtext/test/PluginTestProjectManager.java

@@ -49,7 +49,7 @@ public class PluginTestProjectManager extends XtextTestProjectManager {
 
   // org.eclipse.osgi needed for NLS
   // org.apache.logging.log4j needed for logging in generated StandaloneSetup
-  private static final List<String> REQUIRED_BUNDLES = newArrayList("org.eclipse.xtext.xbase.lib", "org.eclipse.xtend.lib", "org.eclipse.emf.ecore", "com.avaloq.tools.ddk.check.core", "com.avaloq.tools.ddk.check.runtime.core", "com.avaloq.tools.ddk.check.lib", "com.avaloq.tools.ddk.xtext", "org.eclipse.xtext", "org.eclipse.osgi", "org.eclipse.xtend", "org.eclipse.core.runtime", "org.eclipse.xtext.xbase", "org.apache.logging.log4j.api");
+  private static final List<String> REQUIRED_BUNDLES = newArrayList("org.eclipse.xtext.xbase.lib", "org.eclipse.xtend.lib", "org.eclipse.emf.ecore", "com.avaloq.tools.ddk.check.core", "com.avaloq.tools.ddk.check.runtime.core", "com.avaloq.tools.ddk.check.lib", "com.avaloq.tools.ddk.xtext", "org.eclipse.xtext", "org.eclipse.osgi", "org.eclipse.core.runtime", "org.eclipse.xtext.xbase", "org.apache.logging.log4j.api");
 
   private final Injector injector;