Fix build (#1954)

* Fix build

* Update phpstan-baseline.neon

* better fix

Author: staabm

src/Monolog/Handler/BufferHandler.php

@@ -163,7 +163,7 @@ public function getFormatter(): FormatterInterface
         throw new \UnexpectedValueException('The nested handler of type '.\get_class($this->handler).' does not support formatters.');
     }
 
-    public function setHandler(HandlerInterface $handler)
+    public function setHandler(HandlerInterface $handler): void
     {
         $this->handler = $handler;
     }

tests/Monolog/Formatter/ElasticsearchFormatterTest.php

@@ -34,7 +34,7 @@ public function testFormat()
 
         // Expected values
         $expected = $msg->toArray();
-        $expected['datetime'] = '1970-01-01T00:00:00+0000';
+        $expected['datetime'] = '1970-01-01T00:00:00+00:00';
         $expected['context'] = [
             'class' => ['stdClass' => []],
             'foo' => 7,