[DOCS] Fix typos in EXT:dashboard widget documentation

A few minor spelling mistakes and uppercase notation
is changed with this patch.

Releases: main, 12.4, 11.5
Resolves: #103993
Change-Id: Ie71257dcd94e008bff2fd29ca6152152019eedae
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/84467


Tested-by: core-ci <typo3@b13.com>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Oliver Bartsch <bo@cedev.de>