Update monolog

Author: Sudipto Choudhury

composer.json

@@ -18,7 +18,7 @@
         "ext-json": "*",
         "guzzlehttp/guzzle-services": "^1.1",
         "doctrine/inflector": "^1.3|^2.0",
-        "monolog/monolog": "1.12 - 2.1.1"
+        "monolog/monolog": "^1.12|^2.3.5"
     },
     "require-dev": {
         "phpunit/phpunit": "^7.2.0",