build: dont-land gyp-next PRs on LTS branches

gyp-next doesn't support Python 3 anymore so we can't backport its
updates.

PR-URL: #38887
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Beth Griggs <bgriggs@redhat.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jiawen Geng <technicalcute@gmail.com>

.github/label-pr-config.yml

@@ -54,7 +54,7 @@ subSystemLabels:
   /^vcbuild\.bat$/: build, windows, needs-ci
   /^(android-)?configure|node\.gyp|common\.gypi$/: build, needs-ci
   # more specific tools
-  /^tools\/gyp/: tools, build, needs-ci
+  /^tools\/gyp/: tools, build, needs-ci, dont-land-on-v14.x, dont-land-on-v12.x
   /^tools\/doc\//: tools, doc
   /^tools\/icu\//: tools, intl, needs-ci
   /^tools\/(?:osx-pkg\.pmdoc|pkgsrc)\//: tools, macos, install