fix(fab-button): add default padding for fab-button (#17050)

Author: manucorporat

core/src/components/fab-button/fab-button.scss

@@ -10,6 +10,11 @@
   --border-width: 0;
   --border-style: none;
   --border-color: initial;
+  --padding-top: 0;
+  --padding-end: 0;
+  --padding-bottom: 0;
+  --padding-start: 0;
+
   /**
    * @prop --background: Background of the button
    * @prop --background-activated: Background of the button when activated