Remove ruby dependency from mantests

tests/mantest

@@ -3,5 +3,5 @@
 . "${0%/*}/setup" "$@"
 
 # We set PAGER because there's a mantest for `env` that uses it.
-(cd $JQBASEDIR/docs && rake mantests) |
+(cd $JQBASEDIR/docs && pipenv run python3 build_mantests.py) |
     env PAGER=less $VALGRIND $Q $JQ -L "$mods" --run-tests