Fix incorrect error level for deprecation notices

Author: colinodell

CHANGELOG.md

@@ -4,6 +4,10 @@ Updates should follow the [Keep a CHANGELOG](https://keepachangelog.com/) princi
 
 ## [Unreleased][unreleased]
 
+### Fixed
+
+ - Fixed incorrect error level for deprecation notices
+
 ## [1.6.1] - 2021-05-08
 
 ### Fixed

src/CommonMarkConverter.php

@@ -40,7 +40,7 @@ public function __construct(array $config = [], EnvironmentInterface $environmen
         if ($environment === null) {
             $environment = Environment::createCommonMarkEnvironment();
         } else {
-            @\trigger_error(\sprintf('Passing an $environment into the "%s" constructor is deprecated in 1.6 and will not be supported in 2.0; use MarkdownConverter instead', self::class));
+            @\trigger_error(\sprintf('Passing an $environment into the "%s" constructor is deprecated in 1.6 and will not be supported in 2.0; use MarkdownConverter instead', self::class), \E_USER_DEPRECATED);
         }
 
         if ($environment instanceof ConfigurableEnvironmentInterface) {

src/GithubFlavoredMarkdownConverter.php

@@ -27,7 +27,7 @@ public function __construct(array $config = [], EnvironmentInterface $environmen
         if ($environment === null) {
             $environment = Environment::createGFMEnvironment();
         } else {
-            @\trigger_error(\sprintf('Passing an $environment into the "%s" constructor is deprecated in 1.6 and will not be supported in 2.0; use MarkdownConverter instead', self::class));
+            @\trigger_error(\sprintf('Passing an $environment into the "%s" constructor is deprecated in 1.6 and will not be supported in 2.0; use MarkdownConverter instead', self::class), \E_USER_DEPRECATED);
         }
 
         if ($environment instanceof ConfigurableEnvironmentInterface) {