Taxonomy: Remove unnecessary 'All categories' string on Edit Posts and Edit...

Taxonomy: Remove unnecessary 'All categories' string on Edit Posts and Edit Links screens and use taxonomy's `all_items` label instead.

Props johnbillion.
Fixes #36049.
Built from https://develop.svn.wordpress.org/trunk@36808


git-svn-id: https://core.svn.wordpress.org/trunk@36775 1a063a9b-81f0-0310-95a4-ce76da25c4cd