doc: clarify who may land on an LTS staging branch

Current language is a bit confusing

PR-URL: #24465
Refs: #24344 (comment)
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Ali Ijaz Sheikh <ofrobots@google.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

COLLABORATOR_GUIDE.md

@@ -803,9 +803,8 @@ pulled from the staging branch into the LTS branch only when a release is
 being prepared and may be pulled into the LTS branch in a different order
 than they were landed in staging.
 
-Any Collaborator may land commits into a staging branch, but only the release
-team should land commits into the LTS branch while preparing a new
-LTS release.
+Only the members of the @nodejs/backporters team should land commits onto
+LTS staging branches.
 
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