tools: fix example in release proposal linter

`changelog-maker` writes 10 character length short form SHA's.
Explicitly set the `git log format` in the example to match.

PR-URL: https://github.com/nodejs/node/pull/62074
Reviewed-By: Tierney Cyren <hello@bnb.im>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ulises Gascón <ulisesgascongonzalez@gmail.com>
Reviewed-By: Stewart X Addison <sxa@redhat.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

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

@@ -6,6 +6,7 @@
 // Example:
 // $ git log upstream/vXX.x...upstream/vX.X.X-proposal \
 //     --reverse --format='{"prURL":"%(trailers:key=PR-URL,valueonly,separator=)","title":"%s","smallSha":"%h"}' \
+//     --abbrev=10 \
 //   | sed 's/,"title":"Revert "\([^"]\+\)""/,"title":"Revert \\"\1\\""/g' \
 //   | ./lint-release-proposal-commit-list.mjs "path/to/CHANGELOG.md" "$(git rev-parse upstream/vX.X.X-proposal)"