Drop kernel variation of reprotest

With kernel variation, build failed with "kernel too old" error.
8 jobs for master in 32 minutes and 31 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #278552
build

00:04:30

 
  Test
passed #278557
autopkgtest

00:03:59

passed #278558
blhc

00:01:29

passed #278556
lintian

00:02:00

passed #278559
piuparts

00:08:34

failed #278555
reprotest

00:05:48

passed #278554
test-build-all

00:03:50

passed #278553
test-build-any

00:04:07

 
Name Stage Failure
failed
reprotest Test
        if ( cleanup ); then :; else echo >&2 "cleanup failed with exit code $?"; fi;
fi
exit $__x
fi" failed with status 2
Uploading artifacts...
/builds/debian/gdbm/debian/output/reprotest: found 12 matching files
/builds/debian/gdbm/debian/output/reprotest.log: found 1 matching files

Uploading artifacts to coordinator... ok
id=278555 responseStatus=201 Created token=RzcL5xoh
ERROR: Job failed: exit code 1