UriInterface comment return type and actual return type are inconsistent.

[twoodhull]

Several functions' comments in UriInterface state that the return type is null|string, but the declared return type in the signature is a non-nullable string. Are the comments wrong, or should the functions return a nullable string?

Examples:

hack-http-request-response-interfaces/src/UriInterface.hack

Lines 64 to 66 in ab9e095

	* @return null|string The URI scheme.
	*/
	public function getScheme(): string;

hack-http-request-response-interfaces/src/UriInterface.hack

Lines 83 to 85 in ab9e095

	* @return null|string The URI authority, in "[user-info@]host[:port]" format.
	*/
	public function getAuthority(): string;

hack-http-request-response-interfaces/src/UriInterface.hack

Lines 106 to 108 in ab9e095

	* @return null|string The URI host.
	*/
	public function getHost(): string;

hack-http-request-response-interfaces/src/UriInterface.hack

Lines 172 to 174 in ab9e095

	* @return null|string The percent-encoded query string
	*/
	public function getRawQuery(): string;