[BUGFIX] Cache Identifiers shorten the MD5 hash

Cache Identifiers shorten the MD5 hash - This is superfluous substr() work
without any gain - remove it.

Change-Id: I0061337afb74df2f29aae69f868a1a0bbe3ad966
Resolves: #56313
Releases: 6.2
Reviewed-on: https://review.typo3.org/27878
Reviewed-by: Dmitry Dulepov
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn