doc: remove duplicate the from onboarding.md

PR-URL: #17733
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Jon Moss <me@jonathanmoss.me>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

doc/onboarding.md

@@ -107,7 +107,7 @@ onboarding session.
         (especially if it just has nits left).
   * Approving a change
     * Collaborators indicate that they have reviewed and approve of the
-        the changes in a pull request using Github’s approval interface
+        changes in a pull request using Github’s approval interface
     * Some people like to comment `LGTM` (“Looks Good To Me”)
     * You have the authority to approve any other collaborator’s work.
     * You cannot approve your own pull requests.