Create separate Dependabot PRs for JUnit 6 (#3088)

To avoid incompatibilities with native-maven-plugin.

Author: Marcono1234

.github/dependabot.yml

@@ -10,8 +10,13 @@ updates:
       # Name is used for branch name and pull request title
       maven:
         patterns:
-        # Create a single pull request for all dependencies and plugins
-        - "*"
+          # Create a single pull request for all dependencies and plugins
+          - "*"
+        exclude-patterns:
+          # Exclude JUnit 6 from the group (that is, create a separate PR for it)
+          # It is currently only used by `/test-graal-native-image` and frequently causes incompatibilities
+          # there with `org.graalvm.buildtools:native-maven-plugin`, causing the complete Dependabot PR to fail
+          - "org.junit:junit-bom"
 
   - package-ecosystem: "github-actions"
     directory: "/"
@@ -23,5 +28,5 @@ updates:
       # Name is used for branch name and pull request title
       github-actions:
         patterns:
-        # Create a single pull request for all actions
-        - "*"
+          # Create a single pull request for all actions
+          - "*"