Remove Gitter from Composer file.

Author: Maikuolan

composer.json

@@ -7,8 +7,7 @@
         "issues": "https://github.com/phpMussel/Plugin-PHPMailer/issues",
         "source": "https://github.com/phpMussel/Plugin-PHPMailer",
         "docs": "https://github.com/phpMussel/Docs",
-        "rss": "https://github.com/phpMussel/Plugin-PHPMailer/releases.atom",
-        "chat": "https://gitter.im/phpMussel2/Lobby"
+        "rss": "https://github.com/phpMussel/Plugin-PHPMailer/releases.atom"
     },
     "require": {
         "php": ">=7.2.0",