[BUGFIX] EXT:workspaces: Use locallang keys in modal windows

Some modal windows rendered in the workspace management module had
hard-coded strings. This commit replaces such usages with translatable
locallang keys.

Resolves: #103161
Releases: main, 12.4
Change-Id: Id0d6be518abc44b7aab82ebd1312bc159a01898a
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/83050


Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Oliver Bartsch <bo@cedev.de>