update gradle versions

Author: hauner

src/testInt/groovy/io/openapiprocessor/gradle/support/Gradle.groovy

@@ -14,18 +14,20 @@ class Gradle {
         '7.3', '7.3.1', '7.3.2', '7.3.3',
         '7.4', '7.4.1', '7.4.2',
         '7.5', '7.5.1',
-        '7.6', '7.6.1', '7.6.2',
+        '7.6', '7.6.1', '7.6.2', '7.6.3',
         '8.0', '8.0.1', '8.0.2',
         '8.1', '8.1.1',
         '8.2', '8.2.1',
-        '8.3-rc-3'
+        '8.3',
+        '8.4'
     ]
 
     static List<String> VERSIONS_8 = [
         '8.0', '8.0.1', '8.0.2',
         '8.1', '8.1.1',
         '8.2', '8.2.1',
-        '8.3-rc-3'
+        '8.3',
+        '8.4'
     ]
 
     static List<String> VERSIONS_7 = [
@@ -35,6 +37,6 @@ class Gradle {
         '7.3', '7.3.1', '7.3.2', '7.3.3',
         '7.4', '7.4.1', '7.4.2',
         '7.5', '7.5.1',
-        '7.6', '7.6.1', '7.6.2'
+        '7.6', '7.6.1', '7.6.2', '7.6.3'
     ]
 }