[BUGFIX] Button typography

Removes share font from buttons. The current font does
not render adequately.

Change-Id: I8d2a998275e52fbb831abb9046f3711e82acc401
Resolves: #55624
Releases: 6.2
Reviewed-on: https://review.typo3.org/27301
Tested-by: Markus Klein
Reviewed-by: Markus Klein
Reviewed-by: Georg Ringer
Tested-by: Georg Ringer