bazel: Specify nanopb version

Bug: 354274498
Change-Id: Idf637d5ec63df7d48a09a1cbf9b4ba27869a93b4
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/252812
Docs-Not-Needed: Ted Pudlik <tpudlik@google.com>
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
Commit-Queue: Ted Pudlik <tpudlik@google.com>
Reviewed-by: Armando Montanez <amontanez@google.com>

MODULE.bazel

@@ -23,7 +23,10 @@ bazel_dep(name = "bazel_skylib", version = "1.7.1")
 bazel_dep(name = "boringssl", version = "0.20240913.0")
 bazel_dep(name = "freertos", version = "10.5.1.bcr.2")
 bazel_dep(name = "gazelle", version = "0.36.0", repo_name = "bazel_gazelle")
-bazel_dep(name = "nanopb", repo_name = "com_github_nanopb_nanopb")
+
+# Note: the nanopb version specification is a no-op for now, see
+# https://pwbug.dev/354274498#comment32.
+bazel_dep(name = "nanopb", version = "0.4.9.1", repo_name = "com_github_nanopb_nanopb")
 bazel_dep(name = "pico-sdk", version = "2.0.0")
 bazel_dep(name = "picotool", version = "2.0.0")
 bazel_dep(name = "platforms", version = "0.0.10")