style: make "Advanced Options" button's styling similar to its previous "a" element's style

app/assets/javascripts/components/AccountMenu/Authentication.tsx

@@ -280,7 +280,7 @@ const Authentication = observer(({
               <div className="sk-panel-row" />
               <button
                 type="button"
-                className="sn-button small info"
+                className="sk-a info font-bold text-left p-0 hover-text-underline"
                 onClick={() => {
                   setShowAdvanced(!showAdvanced);
                 }}>

app/assets/stylesheets/_sn.scss

@@ -8,6 +8,12 @@
   display: none;
 }
 
+.hover-text-underline {
+  &:hover {
+    text-decoration: underline;
+  }
+}
+
 /**
  * A button that is just an icon. Separated from .sn-button because there
  * is almost no style overlap.