Revert "[gn build] (semi-manually) Port 98aa067109"

This reverts commit 04ce13e497be60f51d340e649c72138d49cb13e9.
The commit message was wrong. Will reland with fixed message.

utils/gn/secondary/clang/include/clang/Tooling/Syntax/BUILD.gn

@@ -1,5 +0,0 @@
-import("//clang/utils/TableGen/clang_tablegen.gni")
-
-clang_tablegen("Nodes") {
-  args = [ "-gen-clang-syntax-node-list" ]
-}

utils/gn/secondary/clang/lib/Tooling/Syntax/BUILD.gn

@@ -2,7 +2,6 @@ static_library("Syntax") {
   output_name = "clangToolingSyntax"
   configs += [ "//llvm/utils/gn/build:clang_code" ]
   deps = [
-    "//clang/include/clang/Tooling/Syntax:Nodes",
     "//clang/lib/Basic",
     "//clang/lib/Frontend",
     "//clang/lib/Lex",

utils/gn/secondary/clang/utils/TableGen/BUILD.gn

@@ -17,7 +17,6 @@ executable("clang-tblgen") {
     "ClangOpenCLBuiltinEmitter.cpp",
     "ClangOptionDocEmitter.cpp",
     "ClangSACheckersEmitter.cpp",
-    "ClangSyntaxEmitter.cpp",
     "ClangTypeNodesEmitter.cpp",
     "MveEmitter.cpp",
     "NeonEmitter.cpp",