Delete unused `--targets_and_headers` flag.

PiperOrigin-RevId: 542814808
diff --git a/rs_bindings_from_cc/cmdline.cc b/rs_bindings_from_cc/cmdline.cc
index 25ee76b..f22885e 100644
--- a/rs_bindings_from_cc/cmdline.cc
+++ b/rs_bindings_from_cc/cmdline.cc
@@ -58,12 +58,6 @@
           "  },\n"
           "...\n"
           "]");
-// Deprecated alias just for migration purposes.
-ABSL_FLAG(std::string, targets_and_headers, "", "DEPRECATED, use target_args")
-    .OnUpdate([] {
-      absl::SetFlag(&FLAGS_target_args,
-                    absl::GetFlag(FLAGS_targets_and_headers));
-    });
 ABSL_FLAG(std::vector<std::string>, extra_rs_srcs, std::vector<std::string>(),
           "Additional Rust source files to include into the crate.");
 ABSL_FLAG(std::vector<std::string>, srcs_to_scan_for_instantiations,