[MNG-6847] Use diamond operator

[timtebeek]

@elharo if you could review once more for https://issues.apache.org/jira/browse/MNG-6847

Use this link to re-run the recipe: https://app.moderne.io/recipes/builder/SEvWu02zw?organizationId=QXBhY2hlIE1hdmVu

[gnodet]

LGTM

[elharo]

Tests might be broken at head. I don't think the failures are caused by this PR but we'll need to resolve that before merging this:

Error: Tests run: 3, Failures: 0, Errors: 2, Skipped: 0, Time elapsed: 0.327 s <<< FAILURE! - in org.apache.maven.it.MavenITmng7038RootdirTest
Error: org.apache.maven.it.MavenITmng7038RootdirTest.testRootdirWithTopdirAndRoot Time elapsed: 0.097 s <<< ERROR!
org.apache.maven.shared.verifier.VerificationException:
Exit code was non-zero: 1; command line and log =
/home/runner/work/maven/maven/maven-integration-testing/core-it-suite/target/apache-maven/bin/mvn -e --batch-mode -Dmaven.repo.local=/home/runner/.m2/repository --global-settings /home/runner/work/maven/maven/maven-integration-testing/core-it-suite/target/test-classes/settings.xml validate
[INFO] Error stacktraces are turned on.
[INFO] Making this build non-interactive, because the environment variable CI equals "true". Disable this detection by removing that variable or adding --force-interactive.
[INFO] Scanning for projects...
Error: Some problems were encountered while processing the POMs
Error: The build could not read 1 project -> [Help 1]

[jira-importer]

Resolve #8447