Revert "add initialized attribute LangRef"

This reverts commit 69a96ae.

Author: haopliu

llvm/docs/LangRef.rst

@@ -1589,23 +1589,6 @@ Currently, only the following parameter attributes are defined:
     ``readonly`` or a ``memory`` attribute that does not contain
     ``argmem: write``.
 
-``initialized((Lo1,Hi1),...)``
-    This attribute is a list of const ranges in ascending order with no
-    overlapping or continuous. It indicates that the function initializes the
-    memory through the pointer argument, [%p+LoN, %p+HiN), and there is no read
-    before initialization in the function. (even though it may read before
-    initializating the memory that the pointer points to).
-
-    The ``writable`` or ``dereferenceable`` attribute does not imply
-    ``initialized`` attribute, however the ``initialized`` argument does imply
-    ``writable`` and ``dereferenceable`` in the specified spaces.
-
-    The ``initialized`` attribute can combine with ``writeonly`` attribute, but
-    cannot be combined with ``readnone``, ``readonly`` or a memory attribute
-    that does not contain ``argmem: write``.
-
-    [TODO: unwind]
-
 ``dead_on_unwind``
     At a high level, this attribute indicates that the pointer argument is dead
     if the call unwinds, in the sense that the caller will not depend on the