test-acl: avoid $HGTMP on windows

sed does not like colons and there are other path normalization issues.

tests/test-acl

@@ -7,7 +7,7 b' do_push()'
 
     echo "Pushing as user $user"
     echo 'hgrc = """'
-    sed -e 1,2d b/.hg/hgrc | grep -v "$HGTMP"
+    sed -e 1,2d b/.hg/hgrc | grep -v fakegroups.py
     echo '"""'
     if test -f acl.config; then
 	echo 'acl.config = """'