tests: fix void and invalid test in test-archive.t

An echo statement was missed in the .t-ification in afe19a1bf9d3 so we ended up
with invalid sh syntax. But at the same time a continuation line was marked as
$ instead of > and we thus added the salt that made the expression valid again.

tests/test-archive.t

@@ -209,8 +209,7 b' rename them afterwards.'
   test-2c0277f05ed4/foo
 
   $ hg archive -r 0 -t tar rev-%r.tar
-  $ if [ -f rev-0.tar ]; then
-  $ fi
+  $ [ -f rev-0.tar ]
 
 test .hg_archival.txt