Remove extra include - fixes bazel build, introduced by 55bef46 (#158037)

Author: basioli-k

clang/lib/Serialization/ASTWriter.cpp

@@ -57,7 +57,6 @@
 #include "clang/Basic/TargetInfo.h"
 #include "clang/Basic/TargetOptions.h"
 #include "clang/Basic/Version.h"
-#include "clang/Frontend/CompilerInstance.h"
 #include "clang/Lex/HeaderSearch.h"
 #include "clang/Lex/HeaderSearchOptions.h"
 #include "clang/Lex/MacroInfo.h"