fix lint issues (#406)

includes/transformer/class-post.php

@@ -357,7 +357,7 @@ class Post {
 
 		$mentions = $this->get_mentions();
 		if ( $mentions ) {
-			foreach ( $mentions as $mention => $url ) {
+			foreach ( $mentions as $url ) {
 				$cc[] = $url;
 			}
 		}

templates/welcome.php

@@ -87,6 +87,7 @@
 			<?php
 			echo wp_kses(
 				\sprintf(
+					/* translators: the placeholder is the Site Health URL */
 					\__(
 						'If you have problems using this plugin, please check the <a href="%s">Site Health</a> page to ensure that your site is compatible and/or use the "Help" tab (in the top right of the settings pages).',
 						'activitypub'