pw_tokenizer: Add missing dep to backwards compatibility target

Change-Id: Icddf65b22acc9ad1fbfc118a0d00715dd795d6ab
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/131112
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
Reviewed-by: Andrei Litvin <andreilitvin@google.com>
Pigweed-Auto-Submit: Wyatt Hepler <hepler@google.com>

pw_tokenizer/BUILD.gn

@@ -118,6 +118,7 @@ pw_source_set("base64") {
 pw_source_set("global_handler_with_payload") {
   public_configs = [ ":public_include_path" ]
   public = [ "public/pw_tokenizer/tokenize_to_global_handler_with_payload.h" ]
+  public_deps = [ dir_pw_preprocessor ]
 }
 
 pw_source_set("decoder") {