Unset the "datetime" parameter in LogglyFormatter

src/Monolog/Formatter/LogglyFormatter.php

@@ -39,7 +39,7 @@ class LogglyFormatter extends JsonFormatter
     {
         if (isset($record["datetime"]) && ($record["datetime"] instanceof \DateTime)) {
             $record["timestamp"] = $record["datetime"]->format("Y-m-d\TH:i:s.uO");
-            // TODO 2.0 unset the 'datetime' parameter, retained for BC
+            unset($record["datetime"]);
         }
 
         return parent::format($record);

tests/Monolog/Formatter/LogglyFormatterTest.php

@@ -34,6 +34,7 @@ class LogglyFormatterTest extends TestCase
         $formatter = new LogglyFormatter();
         $record = $this->getRecord();
         $formatted_decoded = json_decode($formatter->format($record), true);
+        $this->assertArrayNotHasKey("datetime", $formatted_decoded);
         $this->assertArrayHasKey("timestamp", $formatted_decoded);
         $this->assertEquals(new \DateTime($formatted_decoded["timestamp"]), $record["datetime"]);
     }