[BUGFIX] TypoScriptParserTest uses superfluous mock object

TypoScriptParserTest uses superfluous mock object just to
call protected methods but without using mock behaviour.

Change-Id: Iaf8ed0150e63b5da4185dccbcf3dbd5eaa0cf94f
Fixes: #46833
Releases: 6.1
Reviewed-on: https://review.typo3.org/19481
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader