tools: fix failing release-proposal linter for LTS transitions

Author: aduh95

tools/actions/lint-release-proposal-commit-list.mjs

@@ -26,8 +26,12 @@ if (commitListingStart === -1) {
   commitList = changelog.replace(/(^.+\n### Semver-Major|\n### Semver-(Minor|Patch)) Commits\n/gs, '')
     .replaceAll('**(SEMVER-MAJOR)** ', '');
 } else {
-  const commitListingEnd = changelog.indexOf('\n\n<a', commitListingStart);
-  assert.notStrictEqual(commitListingEnd, -1);
+  // We can't assume the Commits section is the one for this release in case of
+  // a release to transition to LTS (i.e. with no commits).
+  const releaseStart = /\n<a id="(\d+\.\d+\.\d+)"><\/a>\n\n## \d+-\d+-\d+, Version \1/.exec(changelog);
+  assert.ok(releaseStart, 'Could not determine the start of the release section');
+  const releaseEnd = changelog.indexOf('\n\n<a', releaseStart.index);
+  assert.notStrictEqual(releaseEnd, -1, 'Could not determine the end of the release section');
   commitList = changelog.slice(commitListingStart, commitListingEnd + 1);
 }