feat(radio): Added screenshot tests to M3 radio.

Other changes:
- Fixed the theme mixin of M3 radio.
- Do not show ripple on keyboard focus.

PiperOrigin-RevId: 447536394

components/radio/lib/_radio-theme.scss

@@ -69,9 +69,8 @@ $light-theme: (
 
 @mixin theme($theme) {
   $theme: theme.validate-theme($light-theme, $theme);
-  @include keys.declare-custom-properties(
-    $theme,
-    $prefix: $custom-property-prefix
+  @include theme.emit-theme-vars(
+    theme.create-theme-vars($theme, $custom-property-prefix)
   );
 }
 

components/radio/lib/radio.ts

@@ -208,15 +208,11 @@ export class Radio extends ActionElement {
   protected handleFocus() {
     this.focused = true;
     this.showFocusRing = shouldShowStrongFocus();
-
-    this.ripple.beginFocus();
   }
 
   protected handleBlur() {
     this.focused = false;
     this.showFocusRing = false;
-
-    this.ripple.endFocus();
   }
 
   protected setFormData(formData: FormData) {