Bump JDT Core to 1.9.21.RC1

Signed-off-by: Alexander Kriegisch <Alexander@Kriegisch.name>

pom.xml

@@ -21,7 +21,7 @@
 		<maven.javadoc.skip>true</maven.javadoc.skip>
 
 		<!-- Dependency versions -->
-		<jdt.core.version>1.9.21-SNAPSHOT</jdt.core.version>
+		<jdt.core.version>1.9.21.RC1</jdt.core.version>
 		<asm.version>9.6</asm.version>
 		<lib.ant.version>1.6.3</lib.ant.version>
 		<lib.ant.xerces.version>2.6.2</lib.ant.xerces.version>