docs: Sphinx conversion is "done"

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@171375 91177308-0d34-0410-b5e6-96231b3b80d8

docs/index.rst

@@ -6,9 +6,6 @@
 Welcome to Clang's documentation!
 =================================
 
-The conversion to Sphinx/reStructuredText based documentation is in
-progress. This page will get filled out with docs soon...
-
 .. toctree::
    :maxdepth: 2