tests: don't run test-update-atomic.t on chg

I am unable to find a good way to make `showwrites` extension in it to work with
chg. Also putting the use of showwrites inside `if no-chg` will defeat the
purpose of test, so I just made the test no-op on chg.

tests/test-update-atomic.t

@@ -1,147 +1,147 b''
-#require execbit unix-permissions
+#require execbit unix-permissions no-chg
 
 Checking that experimental.atomic-file works.
 
   $ cat > $TESTTMP/show_mode.py <<EOF
   > from __future__ import print_function
   > import os
   > import stat
   > import sys
   > ST_MODE = stat.ST_MODE
   > 
   > for file_path in sys.argv[1:]:
   >     file_stat = os.stat(file_path)
   >     octal_mode = oct(file_stat[ST_MODE] & 0o777).replace('o', '')
   >     print("%s:%s" % (file_path, octal_mode))
   > 
   > EOF
 
   $ hg init repo
   $ cd repo
 
   $ cat > .hg/showwrites.py <<EOF
   > from __future__ import print_function
   > from mercurial import pycompat
   > from mercurial.utils import stringutil
   > def uisetup(ui):
   >   from mercurial import vfs
   >   class newvfs(vfs.vfs):
   >     def __call__(self, *args, **kwargs):
   >       print(pycompat.sysstr(stringutil.pprint(
   >           ('vfs open', args, sorted(list(kwargs.items()))))))
   >       return super(newvfs, self).__call__(*args, **kwargs)
   >   vfs.vfs = newvfs
   > EOF
 
   $ for v in a1 a2 b1 b2 c ro; do echo $v > $v; done
   $ chmod +x b*
   $ hg commit -Aqm _
 
 # We check that
 # - the changes are actually atomic
 # - that permissions are correct (all 4 cases of (executable before) * (executable after))
 # - that renames work, though they should be atomic anyway
 # - that it works when source files are read-only (but directories are read-write still)
 
   $ for v in a1 a2 b1 b2 ro; do echo changed-$v > $v; done
   $ chmod -x *1; chmod +x *2
   $ hg rename c d
   $ hg commit -qm _
 
 Check behavior without update.atomic-file
 
   $ hg update -r 0 -q
   $ hg update -r 1 --config extensions.showwrites=.hg/showwrites.py 2>&1 | grep "a1'.*wb"
   ('vfs open', ('a1', 'wb'), [('atomictemp', False), ('backgroundclose', True)])
 
   $ python $TESTTMP/show_mode.py *
   a1:0644
   a2:0755
   b1:0644
   b2:0755
   d:0644
   ro:0644
 
 Add a second revision for the ro file so we can test update when the file is
 present or not
 
   $ echo "ro" > ro
 
   $ hg commit -qm _
 
 Check behavior without update.atomic-file first
 
   $ hg update -C -r 0 -q
 
   $ hg update -r 1
   6 files updated, 0 files merged, 1 files removed, 0 files unresolved
 
   $ python $TESTTMP/show_mode.py *
   a1:0644
   a2:0755
   b1:0644
   b2:0755
   d:0644
   ro:0644
 
 Manually reset the mode of the read-only file
 
   $ chmod a-w ro
 
   $ python $TESTTMP/show_mode.py ro
   ro:0444
 
 Now the file is present, try to update and check the permissions of the file
 
   $ hg up -r 2
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
 
   $ python $TESTTMP/show_mode.py ro
   ro:0644
 
 # The file which was read-only is now writable in the default behavior
 
 Check behavior with update.atomic-files
 
 
   $ cat >> .hg/hgrc <<EOF
   > [experimental]
   > update.atomic-file = true
   > EOF
 
   $ hg update -C -r 0 -q
   $ hg update -r 1 --config extensions.showwrites=.hg/showwrites.py 2>&1 | grep "a1'.*wb"
   ('vfs open', ('a1', 'wb'), [('atomictemp', True), ('backgroundclose', True)])
   $ hg st -A --rev 1
   C a1
   C a2
   C b1
   C b2
   C d
   C ro
 
 Check the file permission after update
   $ python $TESTTMP/show_mode.py *
   a1:0644
   a2:0755
   b1:0644
   b2:0755
   d:0644
   ro:0644
 
 Manually reset the mode of the read-only file
 
   $ chmod a-w ro
 
   $ python $TESTTMP/show_mode.py ro
   ro:0444
 
 Now the file is present, try to update and check the permissions of the file
 
   $ hg update -r 2 --traceback
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
 
   $ python $TESTTMP/show_mode.py ro
   ro:0644
 
 # The behavior is the same as without atomic update