Synced readme with actual definitions (#601)

README.md

@@ -498,7 +498,7 @@ a message.
 
 ## `GuzzleHttp\Psr7\Utils::readLine`
 
-`public static function readLine(StreamInterface $stream, int $maxLength = null): string`
+`public static function readLine(StreamInterface $stream, ?int $maxLength = null): string`
 
 Read a line from the stream up to the maximum allowed buffer length.
 
@@ -674,7 +674,7 @@ termed a relative-path reference.
 
 ### `GuzzleHttp\Psr7\Uri::isSameDocumentReference`
 
-`public static function isSameDocumentReference(UriInterface $uri, UriInterface $base = null): bool`
+`public static function isSameDocumentReference(UriInterface $uri, ?UriInterface $base = null): bool`
 
 Whether the URI is a same-document reference. A same-document reference refers to a URI that is, aside from its
 fragment component, identical to the base URI. When no base URI is given, only an empty URI reference