stablerange: drop unused `until` utility
We no longer needs this function.
# utility to setup pythonpath to point into the tested repositoryexportSRCDIR=`dirname$TESTDIR`if[-n"$PYTHONPATH"];thenexportHGTEST_ORIG_PYTHONPATH=$PYTHONPATHexportPYTHONPATH=$SRCDIR:$PYTHONPATHelseexportPYTHONPATH=$SRCDIRfi