Also remove deprecation warnings when running outside of travis on php 7.4

phpunit.xml.dist

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 
-<phpunit bootstrap="vendor/autoload.php" colors="true">
+<phpunit bootstrap="tests/bootstrap.php" colors="true">
     <testsuites>
         <testsuite name="Monolog Test Suite">
             <directory>tests/Monolog/</directory>

tests/bootstrap.php

@@ -0,0 +1,9 @@
+<?php
+
+if (PHP_VERSION_ID >= 70400) {
+    error_reporting(E_ALL & ~E_DEPRECATED);
+} else {
+    error_reporting(E_ALL);
+}
+
+include __DIR__.'/../vendor/autoload.php';