[TASK] Add Link to wiki page for opcode cache

Add a link to http://wiki.typo3.org/Opcode_Cache in installers
system environment check messages.

Resolves: #56526
Releases: 6.2
Change-Id: If7314d52426729ce092e281697fbbd67bd6ae9d7
Reviewed-on: https://review.typo3.org/28712
Reviewed-by: Markus Klein
Tested-by: Markus Klein
Reviewed-by: Jigal van Hemert
Tested-by: Jigal van Hemert