Fix handling of directories that look like flags in fish (#605)

templates/fish.txt

@@ -82,7 +82,7 @@ function __zoxide_z
         __zoxide_cd -
     else if test $argc -eq 1 -a -d $argv[1]
         __zoxide_cd $argv[1]
-    else if set -l result (string replace --regex $__zoxide_z_prefix_regex '' $argv[-1]); and test -n $result
+    else if set -l result (string replace --regex -- $__zoxide_z_prefix_regex '' $argv[-1]); and test -n $result
         __zoxide_cd $result
     else
         set -l result (command zoxide query --exclude (__zoxide_pwd) -- $argv)