pw_rpc: Remove accidental Python dependency

pw_build is only needed for tests.

Change-Id: I7d27dbfc3d22a4a055b815f147e99c3d4d52a631
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/39988
Pigweed-Auto-Submit: Wyatt Hepler <hepler@google.com>
Reviewed-by: Keir Mierle <keir@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/pw_rpc/py/BUILD.gn b/pw_rpc/py/BUILD.gn
index a8cfc36..07fd6b4 100644
--- a/pw_rpc/py/BUILD.gn
+++ b/pw_rpc/py/BUILD.gn
@@ -49,7 +49,6 @@
     "tests/packets_test.py",
   ]
   python_deps = [
-    "$dir_pw_build/py",
     "$dir_pw_protobuf/py",
     "$dir_pw_protobuf_compiler/py",
     "$dir_pw_status/py",