Merge MC-31679 into 2.3.5-bugfixes-031320

Author: dvoskoboinikov

lib/internal/Magento/Framework/HTTP/PhpEnvironment/Response.php

@@ -191,26 +191,4 @@ public function __sleep()
     {
         return ['content', 'isRedirect', 'statusCode'];
     }
-
-    /**
-     * Sending provided headers.
-     *
-     * Had to be overridden because the original did not work correctly with multi-headers.
-     */
-    public function sendHeaders()
-    {
-        if ($this->headersSent()) {
-            return $this;
-        }
-
-        $status  = $this->renderStatusLine();
-        header($status);
-
-        /** @var \Zend\Http\Header\HeaderInterface $header */
-        foreach ($this->getHeaders() as $header) {
-            header($header->toString(), false);
-        }
-
-        return $this;
-    }
 }