tools: clarify commit message linting

Clarify in Travis results that the commit message linting is for the
commit message and not something else.

PR-URL: https://github.com/nodejs/node/pull/23742
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Vladimir de Turckheim <vlad2t@hotmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>

.travis.yml

@@ -13,7 +13,7 @@ matrix:
       script:
         - make lint
         # Lint the first commit in the PR.
-        - \[ -z "$TRAVIS_COMMIT_RANGE" \] || git log $TRAVIS_COMMIT_RANGE --pretty=format:'%h' --no-merges | tail -1 | xargs npx core-validate-commit --no-validate-metadata
+        - \[ -z "$TRAVIS_COMMIT_RANGE" \] || (echo -e '\nLinting the commit message according to the guidelines at https://goo.gl/p2fr5Q\n' && git log $TRAVIS_COMMIT_RANGE --pretty=format:'%h' --no-merges | tail -1 | xargs npx -q core-validate-commit --no-validate-metadata)
     - name: "Test Suite"
       install:
         - ./configure