Revert change to upgrade notes in #2116 (#2120)

Premature as PR hasn't been submitted yet! This will end up in 4.1 -> 4.2.

docs/source/upgrading/4.0-4.1.rst

@@ -51,14 +51,3 @@ by the application code:
    server.setBodyParser(MIME_FORM_MULTIPART, formMultipartParser);
 
 
-Stream methods
-==============
-
-:pull-request:`1867` added a :cpp:func:`IDataSourceStream::readString(size_t)` method which shadows
-:cpp:func:`Stream::readString`. Its behaviour was also inconsistent in that the stream position
-was left unchanged for memory streams. This has been corrected, and is now a virtual method.
-
-The :c:func:`Stream::readBytes` has been virtualised and overriden for :cpp:class:`IDataSourceStream`
-descendents for more efficient operation, especially with ArduinoJson.
-For normal read operations where the stream position is to be updated, applications should use
-this method in preference to :c:func:`IDataSourceStream::readMemoryBlock`.