Update Ruby version from bump-oss-version.js

Assume the system version is the latest and desired, update all
related files to use that version.

https://circleci.com/docs/2.0/testing-ios/#using-ruby states CircleCI
will use the latest stable version (2.7 at this moment), which is
excellent.

scripts/bump-oss-version.js

@@ -172,6 +172,12 @@ let numberOfChangedLinesWithNewVersion = exec(
   {silent: true},
 ).stdout.trim();
 
+// Make sure to update ruby version
+if (exec('scripts/update-ruby.sh').code) {
+  echo('Failed to update Ruby version');
+  exit(1);
+}
+
 // Release builds should commit the version bumps, and create tags.
 // Nightly builds do not need to do that.
 if (!nightlyBuild) {