doc: fix JS flavor selection

Author: aduh95

doc/api_assets/style.css

@@ -777,7 +777,7 @@ kbd {
 .js-flavor-selector:checked {
  background-image: url(./js-flavor-esm.svg);
 }
-.js-flavor-selector:not(:checked) ~ .esm,
+.js-flavor-selector:not(:checked) ~ .mjs,
 .js-flavor-selector:checked ~ .cjs {
  display: none;
 }