Prevent adding sourceURL to translation script if not printed

It's unclear how the script tag contents may be used by extenders. Avoid
printing the sourceURL if the contents are not immediately printed.

See
https://github.com/WordPress/wordpress-develop/blob/81e3dbeba63838a13b137c6308548e35a616f3b6/src/wp-includes/script-loader.php#L3015.

Author: sirreal

src/wp-includes/class-wp-scripts.php

@@ -722,18 +722,17 @@ public function print_translations( $handle, $display = true ) {
 			return false;
 		}
 
-		$source_url = rawurlencode( "{$handle}-js-translations" );
-
 		$output = <<<JS
 ( function( domain, translations ) {
 	var localeData = translations.locale_data[ domain ] || translations.locale_data.messages;
 	localeData[""].domain = domain;
 	wp.i18n.setLocaleData( localeData, domain );
 } )( "{$domain}", {$json_translations} );
-//# sourceURL={$source_url}
 JS;
 
 		if ( $display ) {
+			$source_url = rawurlencode( "{$handle}-js-translations" );
+			$output    .= "\n//# sourceURL={$source_url}";
 			wp_print_inline_script_tag( $output, array( 'id' => "{$handle}-js-translations" ) );
 		}