test-https: properly conditionalize Windows vs non-Windows output

There's a bug in the (feature !) annotation, and this needs to be resolved
before fixing it.  Once fixed, the glob '*/missing' will match the output
'/missing' on non-Windows platforms, consuming the output line and leaving
nothing for the no-windows required line.

I probably should have made (foo !) match only the 'foo' feature, and be ignored
otherwise instead of optional.  (re) didn't work here, because the parenthesis
need to be escaped too.

tests/test-https.t

@@ -605,14 +605,12 b' Missing certificate file(s) are detected'
 
   $ hg serve -p $HGPORT --certificate=/missing/certificate \
   > --config devel.servercafile=$PRIV --config devel.serverrequirecert=true
-  abort: referenced certificate file (*/missing/certificate) does not exist (glob) (windows !)
-  abort: referenced certificate file (/missing/certificate) does not exist (no-windows !)
+  abort: referenced certificate file (*/missing/certificate) does not exist (glob)
   [255]
 
   $ hg serve -p $HGPORT --certificate=$PRIV \
   > --config devel.servercafile=/missing/cafile --config devel.serverrequirecert=true
-  abort: referenced certificate file (*/missing/cafile) does not exist (glob) (windows !)
-  abort: referenced certificate file (/missing/cafile) does not exist (no-windows !)
+  abort: referenced certificate file (*/missing/cafile) does not exist (glob)
   [255]
 
 Start hgweb that requires client certificates:
@@ -657,14 +655,12 b' with client certificate:'
 Missing certficate and key files result in error
 
   $ hg id https://localhost:$HGPORT/ --config auth.l.cert=/missing/cert
-  abort: certificate file (*/missing/cert) does not exist; cannot connect to localhost (glob) (windows !)
-  abort: certificate file (/missing/cert) does not exist; cannot connect to localhost (no-windows !)
+  abort: certificate file (*/missing/cert) does not exist; cannot connect to localhost (glob)
   (restore missing file or fix references in Mercurial config)
   [255]
 
   $ hg id https://localhost:$HGPORT/ --config auth.l.key=/missing/key
-  abort: certificate file (*/missing/key) does not exist; cannot connect to localhost (glob) (windows !)
-  abort: certificate file (/missing/key) does not exist; cannot connect to localhost (no-windows !)
+  abort: certificate file (*/missing/key) does not exist; cannot connect to localhost (glob)
   (restore missing file or fix references in Mercurial config)
   [255]