[BUGFIX] Show "All" language flag again in Page module (old and Fluid)

Due to the logic being based around SiteLanguages and the "All" language
not being one, it was excluded from being rendered in the content header.

Resolves: #90854
Releases: master, 10.4
Change-Id: I5152cedc80e2b1fd45b6eb626fd635d9be78a29b
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/64125


Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Daniel Haupt <mail@danielhaupt.de>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Daniel Haupt <mail@danielhaupt.de>
Reviewed-by: Benni Mack <benni@typo3.org>