COMPMID-3247: Cleanup README file links

COMPMID-3247: Cleanup README file links

Removed release binaries links. The README now always points to the
GitHub Releases page.

Moved all documentation links to the GitHub Wiki and added a link to
that page in the README.

Change-Id: I9922cc74b14b4192766302f825b1b2af4aa02523
Signed-off-by: Michele Di Giorgio <michele.digiorgio@arm.com>
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/3070
Reviewed-by: Manuel Bottini <manuel.bottini@arm.com>
Reviewed-by: Georgios Pinitas <georgios.pinitas@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Tested-by: Arm Jenkins <bsgcomp@arm.com>