Remove the header-only dep on CodeGen from MCTargetDesc & Utils

Author: rnk

utils/bazel/llvm-project-overlay/llvm/BUILD.bazel

@@ -2270,9 +2270,6 @@ gentbl(
         strip_include_prefix = "lib/Target/" + target["name"],
         deps = [
             ":BinaryFormat",
-            # Depending on `:CodeGen` headers in this library is almost
-            # certainly a layering problem in numerous targets.
-            ":CodeGen",
             ":CodeGenTypes",
             ":DebugInfoCodeView",
             ":MC",