Remove elimination of namespace from closure and escape opening brace

includes/validation/class-amp-validation-manager.php

@@ -1659,7 +1659,7 @@ public static function can_output_buffer() {
 		$called_functions = [];
 		$backtrace        = debug_backtrace( DEBUG_BACKTRACE_IGNORE_ARGS ); // phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_debug_backtrace -- Only way to find out if we are in a buffering display handler.
 		foreach ( $backtrace as $call_stack ) {
-			if ( '{closure}' === $call_stack['function'] ) {
+			if ( '{closure}' === $call_stack['function'] ) { // TODO: This may not be the right format for PHP 8.4.
 				$called_functions[] = 'Closure::__invoke';
 			} elseif ( isset( $call_stack['class'] ) ) {
 				$called_functions[] = sprintf( '%s::%s', $call_stack['class'], $call_stack['function'] );

tests/php/src/TestCase.php

@@ -83,7 +83,7 @@ public function assertIndexedArrayContains( $expected_subset, $actual_superset )
 	public function normalize_closure_function_name( $data ) {
 		if ( is_string( $data ) ) {
 			$data = preg_replace(
-				'/(\w+\\\\)*{closure:[^}]+}/',
+				'/\{closure:[^}]+}/',
 				'{closure}',
 				$data
 			);