chore(deps): bump snappy from 0.3.0 to 0.4.0 in /fluent-plugin-protobuf

Bumps [snappy](https://github.com/miyucy/snappy) from 0.3.0 to 0.4.0.
- [Commits](miyucy/snappy@v0.3.0...v0.4.0)

---
updated-dependencies:
- dependency-name: snappy
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

fluent-plugin-protobuf/Gemfile.lock

@@ -31,7 +31,7 @@ GEM
     serverengine (2.3.2)
       sigdump (~> 0.2.2)
     sigdump (0.2.5)
-    snappy (0.3.0)
+    snappy (0.4.0)
     strptime (0.2.5)
     test-unit (3.6.1)
       power_assert