TrigramIndex.cpp - remove unnecessary includes. NFCI.

TrigramIndex.h already includes most of these.

llvm/include/llvm/Support/TrigramIndex.h

@@ -27,7 +27,7 @@
 #define LLVM_SUPPORT_TRIGRAMINDEX_H
 
 #include "llvm/ADT/SmallVector.h"
-
+#include "llvm/ADT/StringRef.h"
 #include <string>
 #include <unordered_map>
 #include <vector>

llvm/lib/Support/TrigramIndex.cpp

@@ -15,12 +15,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Support/TrigramIndex.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/StringRef.h"
-
 #include <set>
-#include <string>
-#include <unordered_map>
 
 using namespace llvm;