Fix typo.

llvm-svn: 248807
diff --git a/clang/lib/Lex/Preprocessor.cpp b/clang/lib/Lex/Preprocessor.cpp
index 82fcde5..f410ad7 100644
--- a/clang/lib/Lex/Preprocessor.cpp
+++ b/clang/lib/Lex/Preprocessor.cpp
@@ -716,7 +716,7 @@
 }
 
 void Preprocessor::Lex(Token &Result) {
-  // We loop here until a lex function retuns a token; this avoids recursion.
+  // We loop here until a lex function returns a token; this avoids recursion.
   bool ReturnedToken;
   do {
     switch (CurLexerKind) {