fix: Properly remove focus from the last focused widget

The previous implementation did not remove focus from the last focused
widget when another widget was focused. This caused visual inconsistencies,  such as the caret in the search bar persisting even after focus was stolen by another widget. Updated `AbstractFrame::setFocused` to ensure the focus state of the previous widget is cleared correctly.

Fixes #123

common/src/main/java/me/flashyreese/mods/reeses_sodium_options/client/gui/frame/AbstractFrame.java

@@ -79,6 +79,9 @@ public GuiEventListener getFocused() {
 
     @Override
     public void setFocused(@Nullable GuiEventListener focused) {
+        if (this.focused != null) {
+            this.focused.setFocused(false);
+        }
         this.focused = focused;
         if (this.focusListener != null) {
             this.focusListener.accept(focused);