build(deps): bump sigstore-protobuf-specs from 0.3.2 to 0.3.4

Bumps [sigstore-protobuf-specs](https://github.com/sigstore/protobuf-specs) from 0.3.2 to 0.3.4.
- [Release notes](https://github.com/sigstore/protobuf-specs/releases)
- [Changelog](https://github.com/sigstore/protobuf-specs/blob/main/CHANGELOG.md)
- [Commits](sigstore/protobuf-specs@v0.3.2...release/rust/v0.3.4)

---
updated-dependencies:
- dependency-name: sigstore-protobuf-specs
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

pyproject.toml

@@ -38,7 +38,7 @@ dependencies = [
   "rfc8785 ~= 0.1.2",
   "rfc3161-client >= 0.1.2,< 1.1.0",
   # NOTE(ww): Both under active development, so strictly pinned.
-  "sigstore-protobuf-specs == 0.3.2",
+  "sigstore-protobuf-specs == 0.3.4",
   "sigstore-rekor-types == 0.0.18",
   "tuf ~= 5.0",
   "platformdirs ~= 4.2",