[TASK] Remove the "Enable Install Tool" button

The "Enable Install Tool" button in the User Settings is useless, as the
Install Tool is automatically enabled (after request) since #28621
and #28689.

Change-Id: I596a0b45d9b947e58b30e0082f23413b56e6f325
Resolves: #29996
Releases: 4.6
Reviewed-on: http://review.typo3.org/5040
Reviewed-by: Jigal van Hemert
Tested-by: Jigal van Hemert
Reviewed-by: Helmut Hummel
Tested-by: Helmut Hummel