[TASK] Remove duplicate calls to substr in InfoPageTyposcriptConfigController

substr is called 3 times with the same parameters, use one variable for this.

Resolves: #78583
Releases: master
Change-Id: Idc57e143c26cd190f8047d59f1e36cb745e9aaf8
Reviewed-on: https://review.typo3.org/50514


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Tymoteusz Motylewski <t.motylewski@gmail.com>
Tested-by: Tymoteusz Motylewski <t.motylewski@gmail.com>