Use JDK 18 GA instead of 18 EA

JDK 18 is now released, use the GA version instead
of EA in build matrix.

Author: plamentotev

.github/workflows/maven.yml

@@ -35,7 +35,7 @@ on:
       jdk-matrix:
         description: 'jdk matrix as json array'
         required: false
-        default: '[ "8", "11", "17", "18-ea" ]'
+        default: '[ "8", "11", "17", "18" ]'
         type: string
 
       matrix-exclude: