Remove references to MODE_NO_COMPRESSION

MODE_NO_COMPRESSION doesn't exist, but the documentation claimed it did. The real spelling is OP_NO_COMPRESSION, but that is already documented.

Closes #60.
diff --git a/doc/api/ssl.rst b/doc/api/ssl.rst
index b506757..da7cfb7 100644
--- a/doc/api/ssl.rst
+++ b/doc/api/ssl.rst
@@ -83,12 +83,6 @@
     :py:const:`OP_NO_*` constant may be undefined.
 
 
-.. py:data:: MODE_NO_COMPRESSION
-
-   Constant used with :py:meth:`set_mode` of Context objects to disable
-   automatic compression of application traffic.
-
-
 .. py:data:: SSLEAY_VERSION
              SSLEAY_CFLAGS
              SSLEAY_BUILT_ON