Fix spoiler buttons css not rendering correct color in light theme (#19960)

* Updating status__content__spoiler-link css for mastodon-light theme to ensure correct rendering precedence

* Adding focus css selector to status__content__spoiler-link mastodon-light theme

* reformatting code to match convention of having css selectors on separate lines

* fixing code format for  scss linting issue

app/javascript/styles/mastodon-light/diff.scss

@@ -268,7 +268,8 @@ html {
 .status__content .status__content__spoiler-link {
   background: $ui-base-color;
 
-  &:hover {
+  &:hover,
+  &:focus {
     background: lighten($ui-base-color, 4%);
   }
 }