llvm docs: drop index.rst release version warning

Author: zmodem

llvm/docs/index.rst

@@ -1,11 +1,6 @@
 About
 ========
 
-.. warning::
-
-   If you are using a released version of LLVM, see `the download page
-   <http://llvm.org/releases/>`_ to find your documentation.
-
 The LLVM compiler infrastructure supports a wide range of projects, from
 industrial strength compilers to specialized JIT applications to small
 research projects.