system/HTTP/Message.php
public function removeHeader(string $name)
	{
		$orig_name = $this->getHeaderName($name);

		unset($this->headers[$orig_name]);
		unset($this->headerMap[strtolower($name)]);

		return $this;
	}
public function removeHeader(string $name)
	{
		$orig_name = $this->getHeaderName($name);

		unset($this->headers[$orig_name]);
		unset($this->headerMap[strtolower($name)]);

		return $this;
	}
Removes a header from the list of headers we track.

@param string $name

@return Message