core/mount: remove "fail" again

deb6120920 'man: there's actually no "fail" fstab option, but only
"nofail" removed it from our documentation, which I missed.
fstab(5) only mentions "auto", "noauto", and "nofail". Stick to
those three.

(cherry picked from commit 76c37ab6d2)

src/core/mount.c

@@ -902,7 +902,7 @@ static void mount_enter_mounting(Mount *m) {
                 _cleanup_free_ char *opts = NULL;
 
                 r = fstab_filter_options(m->parameters_fragment.options,
-                                         "nofail\0" "fail\0" "noauto\0" "auto\0", NULL, NULL, &opts);
+                                         "nofail\0" "noauto\0" "auto\0", NULL, NULL, &opts);
                 if (r < 0)
                         goto fail;