tests: Switch emoji used

widechar_width no longer classifies U+1F41F as widened-in-9, so the
width no longer changes.

Since we're interested in testing the change here, we need a different
emoji.

Just use 🥁, which was introduced in 9 as wide, and therefore widened
in 9.

tests/checks/string.fish

@@ -93,11 +93,11 @@ string length --visible (set_color red)abc
 begin
     set -l fish_emoji_width 2
     # This should print the emoji width
-    string length --visible . 🐟
+    string length --visible . 🥁
     # CHECK: 1
     # CHECK: 2
     set -l fish_emoji_width 1
-    string length --visible . 🐟
+    string length --visible . 🥁
     # CHECK: 1
     # CHECK: 1
 end