Update wordpress-coding-standards/php.md

Co-authored-by: Stephen Edgar <stephen@netweb.com.au>

Author: dingo-d

wordpress-coding-standards/php.md

@@ -391,7 +391,7 @@ Files containing template tags in `wp-includes` should have `-template` appended
 general-template.php
 ```
 
-### Only one object structure (class/interface/trait) should be declared per file
+### Only one object structure (class/interface/trait) declared per file
 
 For instance, if we have a file called `class-example-class.php` it can only contain one class in that file.