use release 11 to comply with the plan

Signed-off-by: Lukas Jungmann <lukas.jungmann@oracle.com>
diff --git a/api/pom.xml b/api/pom.xml
index 0eda3d3..93c1b6d 100644
--- a/api/pom.xml
+++ b/api/pom.xml
@@ -98,7 +98,7 @@
         <vendor.name>Eclipse Foundation</vendor.name>
         <implementation.vendor.id>org.glassfish</implementation.vendor.id>
 
-        <maven.compiler.release>21</maven.compiler.release>
+        <maven.compiler.release>11</maven.compiler.release>
     </properties>
 
     <build>