test-tags: enable for Windows

It turns out that MSYS does have a chmod.exe, but it has no effect. So, the
inserted "#if unix-permissions" is somewhat redundant, as the test would pass
without it as well: it would simply write the tag cache, despite what the
comment says.

But I'm actually in favor of inserting the #if, as it makes it clearer what's
going on.

tests/test-tags.t

@@ -1,5 +1,3 b''
-  $ "$TESTDIR/hghave" unix-permissions || exit 80
-
 Helper functions:
 
   $ cacheexists() {
@@ -77,11 +75,13 b' Repeat with cold tag cache:'
 
 And again, but now unable to write tag cache:
 
+#if unix-permissions
   $ rm -f .hg/cache/tags
   $ chmod 555 .hg
   $ hg identify
   b9154636be93 tip
   $ chmod 755 .hg
+#endif
 
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