Coding Standards: Replace the old wp-db.php filename in `phpcompat.…

…xml.dist`.

This ensures the correct file is allowlisted for use of `mysql_` extension in PHP < 7.0.

Follow-up to [53749].

See #56268, #55647.

git-svn-id: https://develop.svn.wordpress.org/trunk@53750 602fd350-edb4-49c9-b593-d223f7449a82

phpcompat.xml.dist

@@ -84,6 +84,6 @@
 
 	<!-- Whitelist the WP DB Class for use of `mysql_` extension in PHP < 7.0. -->
 	<rule ref="PHPCompatibility.Extensions.RemovedExtensions.mysql_DeprecatedRemoved">
-		<exclude-pattern>/src/wp-includes/wp-db\.php</exclude-pattern>
+		<exclude-pattern>/src/wp-includes/class-wpdb\.php</exclude-pattern>
 	</rule>
 </ruleset>