Rename .follow-button to .button--follow

The other classname is listed on Fanboy's Annoyances List

app/soapbox/features/ui/components/action_button.js

@@ -104,7 +104,7 @@ class ActionButton extends ImmutablePureComponent {
         // Follow & Unfollow
         return (<Button
           disabled={account.getIn(['relationship', 'blocked_by'])}
-          className={classNames('follow-button', {
+          className={classNames('button--follow', {
             'button--destructive': account.getIn(['relationship', 'following']),
           })}
           onClick={this.handleFollow}

app/styles/components/buttons.scss

@@ -143,7 +143,7 @@ a.button {
   }
 }
 
-.follow-button {
+.button--follow {
   display: flex;
   align-items: center;
   justify-content: center;