[TASK] Make use of .t3-table in ShowItem (i) window

Also remove one unused css style.

Change-Id: I4a8ccf3861d3e49b4fdab7d542fe2024c5f02f93
Resolves: #55482
Releases: 6.2
Reviewed-on: https://review.typo3.org/27171
Reviewed-by: Wouter Wolters
Reviewed-by: Benjamin Mack
Tested-by: Benjamin Mack