hush: remove test for "echo ${-}" errorring out - now it works

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

shell/ash_test/ash-vars/param_expand_default.tests

@@ -1,6 +1,5 @@
 # first try some invalid patterns (do in subshell due to parsing error)
 # (set argv0 to "SHELL" to avoid "/path/to/shell: blah" in error messages)
-# valid in bash and ash (same as $-): "$THIS_SH" -c 'echo ${-}' SHELL
 "$THIS_SH" -c 'echo ${:-}' SHELL
 
 # now some funky ones