[TASK] Increase Extension Manager->showConfiguration input field width

Increases the width of string input fields to 300 pixels.

Resolves: #59679
Releases: 6.2, 6.3
Change-Id: Ia415a6cdf81e4f6192a7e3fb93d8f01d8a749c6a
Reviewed-on: https://review.typo3.org/30905
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters