Remove unused headers from WebAssemblyToolchains

Author: MaxDesiatov

lib/Driver/WebAssemblyToolChains.cpp

@@ -14,11 +14,9 @@
 
 #include "swift/ABI/System.h"
 #include "swift/AST/DiagnosticsDriver.h"
-#include "swift/Basic/Dwarf.h"
 #include "swift/Basic/LLVM.h"
 #include "swift/Basic/Platform.h"
 #include "swift/Basic/Range.h"
-#include "swift/Basic/TaskQueue.h"
 #include "swift/Config.h"
 #include "swift/Driver/Compilation.h"
 #include "swift/Driver/Driver.h"