Remove variable output affected by length of TMPDIR.

If the temporary directory is longer than /tmp then it's possible that
the Subject line will get wrapped by the headencode function.

tests/test-notify-changegroup

@@ -10,7 +10,7 b' changegroup.notify = python:hgext.notify'
 [notify]
 sources = push
 diffstat = False
-maxsubject = 200
+maxsubject = 10
 
 [usersubs]
 foo@bar = *
@@ -37,7 +37,7 b' hg --traceback --cwd b push ../a 2>&1 |'
     python -c 'import sys,re; print re.sub("\n\t", " ", sys.stdin.read()),' |
     sed -e 's/\(Message-Id:\).*/\1/' \
         -e 's/changeset \([0-9a-f]* *\)in .*test-notif/changeset \1in test-notif/' \
-        -e 's/^Subject: .*test-notify/Subject: test-notify/' \
+        -e 's/^Subject: .*/Subject: test-notify-changegroup/' \
         -e 's/^details: .*test-notify/details: test-notify/' \
         -e 's/^Date:.*/Date:/'
 

tests/test-notify-changegroup.out

@@ -15,7 +15,7 b' Content-Type: text/plain; charset="us-as'
 MIME-Version: 1.0
 Content-Transfer-Encoding: 7bit
 Date:
-Subject: test-notify-changegroup/a: 2 new changesets
+Subject: test-notify-changegroup
 From: test
 X-Hg-Notification: changeset cb9a9f314b8b
 Message-Id: