doc: update base branch name for nodejs/nodejs.org

PR-URL: nodejs#42355
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: Mestery <mestery@protonmail.com>

doc/contributing/releases.md

@@ -692,8 +692,9 @@ This script will use the promoted builds and changelog to generate the post. Run
   Refs: <full URL to your release proposal PR>
   ```
 
-* Changes to `master` on the [nodejs.org repository][] will trigger a new build
-  of nodejs.org so your changes should appear a few minutes after pushing.
+* Changes to the base branch, `main`, on the [nodejs.org repository][] will
+  trigger a new build of nodejs.org so your changes should appear a few minutes
+  after pushing.
 
 ### 18. Create the release on GitHub