doc: remove outdated COLLABORATOR_GUIDE sentence about breaking changes

The TSC has delegated authority over LTS and Current branches to the
Release WG. Remove the bullet point about TSC having authority to
determine that a breaking change is necessary on LTS and Current release
branches. Retaining that authority would require de-chartering the
Release WG.

Fixes: nodejs/TSC#660

COLLABORATOR_GUIDE.md

@@ -282,7 +282,6 @@ providing a Public API in such cases.
   * Resolving critical security issues.
   * Fixing a critical bug (e.g. fixing a memory leak) requires a breaking
     change.
-  * There is TSC consensus that the change is required.
 * If a breaking commit does accidentally land in a Current or LTS branch, an
   attempt to fix the issue will be made before the next release; If no fix is
   provided then the commit will be reverted.