[LTO] Remove unused includes (NFC) (llvm#108110)

clangd reports these as unused headers.  My manual inspection agrees
with the findings.

Author: kazutakahirata

llvm/include/llvm/LTO/LTO.h

@@ -19,7 +19,6 @@
 
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/MapVector.h"
-#include "llvm/ADT/StringMap.h"
 #include "llvm/Bitcode/BitcodeReader.h"
 #include "llvm/IR/ModuleSummaryIndex.h"
 #include "llvm/LTO/Config.h"

llvm/include/llvm/Transforms/IPO/FunctionImport.h

@@ -17,9 +17,7 @@
 #include "llvm/IR/PassManager.h"
 #include "llvm/Support/Error.h"
 #include <functional>
-#include <map>
 #include <memory>
-#include <string>
 #include <system_error>
 #include <utility>
 

llvm/lib/LTO/LTO.cpp

@@ -38,7 +38,6 @@
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/FileSystem.h"
-#include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/SHA1.h"

llvm/lib/Transforms/IPO/FunctionImport.cpp

@@ -46,7 +46,6 @@
 #include "llvm/Transforms/Utils/ValueMapper.h"
 #include <cassert>
 #include <memory>
-#include <set>
 #include <string>
 #include <system_error>
 #include <tuple>