Fix mirroring of effect icons for RTL

src/components/sound-editor/sound-editor.css

@@ -172,12 +172,16 @@ $border-radius: 0.25rem;
     margin-bottom: -0.375rem;
 }
 
-/* mirror the louder/softer speaker icons when rtl */
-[dir="rtl"] .effect-button:nth-of-type(6) img {
+/* mirror the louder/softer/mute speaker icons when rtl */
+[dir="rtl"] .effect-button:nth-of-type(4) img {
     transform: scaleX(-1);
 }
 
-[dir="rtl"] .effect-button:nth-of-type(7) img {
+[dir="rtl"] .effect-button:nth-of-type(5) img {
+    transform: scaleX(-1);
+}
+
+[dir="rtl"] .effect-button:nth-of-type(6) img {
     transform: scaleX(-1);
 }