deps: update dependency com.google.protobuf:protobuf-bom to v3.11.4

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [com.google.protobuf:protobuf-bom](https://developers.google.com/protocol-buffers/) ([source](https://togithub.com/protocolbuffers/protobuf)) | patch | `3.11.3` -> `3.11.4` |

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### Release Notes

<details>
<summary>protocolbuffers/protobuf</summary>

### [`v3.11.4`](https://togithub.com/protocolbuffers/protobuf/releases/v3.11.4)

[Compare Source](https://togithub.com/protocolbuffers/protobuf/compare/v3.11.3...v3.11.4)

# C#

-   Fix latest ArgumentException for C# extensions ([#&#8203;7188](https://togithub.com/protocolbuffers/protobuf/issues/7188))
-   Enforce recursion depth checking for unknown fields ([#&#8203;7210](https://togithub.com/protocolbuffers/protobuf/issues/7210))

# Ruby

-   Fix wrappers with a zero value ([#&#8203;7195](https://togithub.com/protocolbuffers/protobuf/issues/7195))
-   Fix JSON serialization of 0/empty-valued wrapper types ([#&#8203;7198](https://togithub.com/protocolbuffers/protobuf/issues/7198))

</details>

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Author: renovate-bot

pom.xml

@@ -68,7 +68,7 @@
     <google.common-protos.version>1.17.0</google.common-protos.version>
     <gax.version>1.53.1</gax.version>
     <grpc.version>1.27.0</grpc.version>
-    <protobuf.version>3.11.3</protobuf.version>
+    <protobuf.version>3.11.4</protobuf.version>
     <junit.version>4.13</junit.version>
     <guava.version>28.2-android</guava.version>
     <threeten.version>1.4.1</threeten.version>