Make spatial audio Firefox-only

Hopefully explained in comment: we have a heisenbug where we sometimes
lack audio from a certain participant, so this simplifies the audio
path by removing the workaround required to do AEC with spatial audio
on chrome.

src/input/Input.module.css

@@ -151,6 +151,15 @@
   margin-right: 10px;
 }
 
+.checkboxField.disabled,
+.checkboxField.disabled .description {
+  color: var(--quinary-content);
+}
+
+.checkboxField.disabled .checkbox {
+  border-color: var(--quinary-content);
+}
+
 .checkbox svg {
   display: none;
 }