Fixed wrong jdk versions

Author: marcingrzejszczak

.github/workflows/maven.yml

@@ -5,9 +5,9 @@ name: Build
 
 on:
   push:
-    branches: [ master ]
+    branches: [ main ]
   pull_request:
-    branches: [ master ]
+    branches: [ main ]
 
 jobs:
   build:

src/main/groovy/org/springframework/jenkins/common/job/JdkConfig.groovy

@@ -11,11 +11,11 @@ import groovy.transform.CompileStatic
 trait JdkConfig {
 
 	String jdk16() {
-		return "openjdk15"
+		return "openjdk16"
 	}
 
 	String jdk15() {
-		return "openjdk16"
+		return "openjdk15"
 	}
 
 	String jdk14() {