Add [staff_profile] shortcode for backward compatibility with sites already using [staff]

includes/admin/post-types/meta-boxes/class-sp-meta-box-staff-shortcode.php

@@ -23,7 +23,7 @@ class SP_Meta_Box_Staff_Shortcode {
 		<p class="howto">
 			<?php _e( 'Copy this code and paste it into your post, page or text widget content.', 'sportspress' ); ?>
 		</p>
-		<p><input type="text" value="<?php sp_shortcode_template( 'staff', $post->ID ); ?>" readonly="readonly" class="code widefat"></p>
+		<p><input type="text" value="<?php sp_shortcode_template( 'staff_profile', $post->ID ); ?>" readonly="readonly" class="code widefat"></p>
 		<?php
 	}
 }