[BUGFIX] Updating deactivated extensions installs them

If you update a deactivated extension it becomes activated afterwards.
This patch change from the installExtension function to
downloadMainExtension function because on updates it is enough to
download the new extension.

Resolves: #59631
Releases: 6.3, 6.2
Change-Id: Idec8c1f3521fa03241def5e171718b42cc31ce6b
Reviewed-on: https://review.typo3.org/31348
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters