Update install docs for suppoted versions of OpenSSL (#813)

Author: alex

INSTALL.rst

@@ -28,11 +28,7 @@ Currently that means:
 - 1.0.1
 - 1.0.2
 - 1.1.0
-
-If you need support for older releases, the following pinned versions will work:
-
-- **OpenSSL 0.9.8**: ``'pyOpenSSL<17.0' 'cryptography<1.4'``
-- **OpenSSL 1.0.0**: ``'pyOpenSSL<17.1' 'cryptography<1.7'``
+- 1.1.1
 
 You can always find out the versions of pyOpenSSL, cryptography, and the linked OpenSSL by running ``python -m OpenSSL.debug``.