[BUGFIX] Prevent go back by submit on enter

The first button of type=submit is used by the browser if
the user hint <enter> in a form field. A form should only contains
one submit button, which is fixed now with this patch.

Resolves: #82668
Releases: master, 8.7
Change-Id: I43323dd89be67d18a2818faf11359151223458f1
Reviewed-on: https://review.typo3.org/54282


Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Joerg Boesche <typo3@joergboesche.de>
Reviewed-by: Markus Sommer <markus.sommer@typo3.org>
Tested-by: Markus Sommer <markus.sommer@typo3.org>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>