tests: make test-alias.t pass with re2

Locally, these "non-ASCII character in alias" errors don't show up,
though I get them when the alias is defined at the command line rather
than in an hgrc.
The brokenness comes from the fact that hgrcs are parsed with regexes,
and re/re2 differ in this way:

$ python -c 'import re; print(re.compile("(.*)").match("aaa\xc0bbbb").groups())'
('aaa\xc0bbbb',)
$ python -c 'import re2; print(re2.compile("(.*)").match("aaa\xc0bbbb").groups())'
('aaa',)

Apparently re2 stops when it encounters invalid utf8 (which I suppose makes sense
given that '.' matches what appears to be a codepoint rather than a byte). This is
presumably a bug in hg, but not very important, so just change the test to stick
to valid utf8.

Differential Revision: https://phab.mercurial-scm.org/D5288

tests/test-alias.t

@@ -623,9 +623,9 b' invalid character in user-specified help'
   >>> with open('.hg/hgrc', 'ab') as f:
   ...     f.write(b'[alias]\n'
   ...             b'invaliddoc = log\n'
-  ...             b'invaliddoc:doc = \xc0\n'
+  ...             b'invaliddoc:doc = \xc3\xa9\n'
   ...             b'invalidhelp = log\n'
-  ...             b'invalidhelp:help = \xc0\n') and None
+  ...             b'invalidhelp:help = \xc3\xa9\n') and None
   $ hg help invaliddoc
   non-ASCII character in alias definition 'invaliddoc:doc'
   $ hg help invalidhelp