[NFC] fix trivial typos in comments and documents

"in in" -> "in", "on on" -> "on" etc.

llvm-svn: 323509
diff --git a/clang/lib/CodeGen/CGObjC.cpp b/clang/lib/CodeGen/CGObjC.cpp
index 1e022f0..43f34e7 100644
--- a/clang/lib/CodeGen/CGObjC.cpp
+++ b/clang/lib/CodeGen/CGObjC.cpp
@@ -2071,7 +2071,7 @@
 
 /// Claim a possibly-autoreleased return value at +0.  This is only
 /// valid to do in contexts which do not rely on the retain to keep
-/// the object valid for for all of its uses; for example, when
+/// the object valid for all of its uses; for example, when
 /// the value is ignored, or when it is being assigned to an
 /// __unsafe_unretained variable.
 ///