fix(b-avatar): fix button type font size inheritance (#5177)

Author: tmorehouse

src/components/avatar/_avatar.scss

@@ -5,6 +5,7 @@
   align-items: center;
   justify-content: center;
   vertical-align: middle;
+  font-size: inherit;
   font-weight: 400;
   line-height: 1;
   max-width: 100%;