tests: adjust recent changes to virtual memory limits

tests: adjust recent changes to virtual memory limits

* tests/dd/no-allocate.sh: Account for timeout(1) when
determining the required mem, as timeout has additional shared libs.
This avoids the need for the hardcoded 4M addition to the limit.
* tests/misc/head-c.sh: Increase the base limit, to account for
the fact that head(1) will allocate some additional mem in this case.
* tests/misc/cut-huge-range.sh: Remove mention of specific limits.
* tests/misc/printf-surprise.sh: Likewise.
Reported by Dmitry V. Levin