Relax wording about published wheels

We publish whatever cibuildwheel builds, so let's not be explicit about
which platforms and python versions we build wheels for.

Signed-off-by: Rodrigo Tobar <rtobar@icrar.org>

README.rst

@@ -41,8 +41,8 @@ Ijson is hosted in PyPI, so you should be able to install it via ``pip``::
   pip install ijson
 
 Binary wheels are provided
-for major platforms (Linux, MacOS, Windows)
-and python versions (2.7, 3.5+).
+for major platforms
+and python versions.
 These are built and published automatically
 using `cibuildwheel <https://cibuildwheel.readthedocs.io/en/stable/>`_
 via Travis CI.