chore: Add Ruby agent team codeowners to Ruby docs

This adds @newrelic/ruby-agent team to notifications whenever a Ruby agent-related file is changed.
Also, it removes an extra space from the "Whats new" section.

.github/CODEOWNERS

@@ -14,5 +14,7 @@ yarn.lock @newrelic/docs-engineering
 /scripts/ @newrelic/docs-engineering
 
 # Whats new files (pings individual project marketing managers)
-
 /src/content/whats-new/ @john-withers @aalfano7
+
+# Ruby agent docs
+**/ruby* @newrelic/ruby-agent