[roll third_party/pigweed] pw_rpc: Remove the public interface to ServerContext

ServerContext is unnecessary and will be removed. All information in the
ServerContext is available in the ServerReader/Writer object.

Remove the only public method on ServerContext& to simplify the eventual
deprecation and removal.

Original-Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/60442

https://pigweed.googlesource.com/pigweed/pigweed
third_party/pigweed Rolled-Commits: 2a02c511260e7d0..ebf33b70f8fc2db
Roller-URL: https://ci.chromium.org/b/8836085652606444337
Cq-Cl-Tag: roller-builder:pigweed-sample-project-roller
Cq-Cl-Tag: roller-bid:8836085652606444337
CQ-Do-Not-Cancel-Tryjobs: true
Change-Id: I274542656fa02348a2b6dcb6ed8fa388e3540bea
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/sample_project/+/60961
Bot-Commit: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
Commit-Queue: Pigweed Integration Roller <pigweed-integration-roller@pigweed.google.com.iam.gserviceaccount.com>
diff --git a/third_party/pigweed b/third_party/pigweed
index 2a02c51..ebf33b7 160000
--- a/third_party/pigweed
+++ b/third_party/pigweed
@@ -1 +1 @@
-Subproject commit 2a02c511260e7d0651de4fccc9cf0d1d2fa8b6cc
+Subproject commit ebf33b70f8fc2db0d5561f5547bc9c2fac18f311