*/gimp-help*: Mark MAKE_JOBS_UNSAFE

The build of the non-English slave ports can fail randomly when
building in parallel. Mark the master port (misc/gimp-help-en)
MAKE_JOBS_UNSAFE to work around this.

• Drop 'The' prefix from COMMMENT in the slave ports while here

PR: 226054, 226189
Submitted by: maintainer
Reported by: truckman