deps: update dependency com.google.cloud:grpc-gcp to v1.2.1 (#751)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [com.google.cloud:grpc-gcp](https://togithub.com/GoogleCloudPlatform/grpc-gcp-java) | `1.1.0` -> `1.2.1` | [![age](https://badges.renovateapi.com/packages/maven/com.google.cloud:grpc-gcp/1.2.1/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.cloud:grpc-gcp/1.2.1/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.cloud:grpc-gcp/1.2.1/compatibility-slim/1.1.0)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.cloud:grpc-gcp/1.2.1/confidence-slim/1.1.0)](https://docs.renovatebot.com/merge-confidence/) |

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### Release Notes

<details>
<summary>GoogleCloudPlatform/grpc-gcp-java</summary>

### [`v1.2.1`](https://togithub.com/GoogleCloudPlatform/grpc-gcp-java/releases/tag/v1.2.1)

[Compare Source](https://togithub.com/GoogleCloudPlatform/grpc-gcp-java/compare/v1.2.0...v1.2.1)

##### Dependencies

-   protobuf 3.12.0 -> 3.20.1

### [`v1.2.0`](https://togithub.com/GoogleCloudPlatform/grpc-gcp-java/releases/tag/v1.2.0)

[Compare Source](https://togithub.com/GoogleCloudPlatform/grpc-gcp-java/compare/v1.1.0...v1.2.0)

##### Features

-   multi-endpoint ([#&#8203;135](https://togithub.com/GoogleCloudPlatform/grpc-gcp-java/issues/135)).
-   round-robin for bind calls ([#&#8203;127](https://togithub.com/GoogleCloudPlatform/grpc-gcp-java/issues/127)).
-   minSize of the channel pool ([#&#8203;134](https://togithub.com/GoogleCloudPlatform/grpc-gcp-java/issues/134)).
-   detailed logs ([#&#8203;133](https://togithub.com/GoogleCloudPlatform/grpc-gcp-java/issues/133)).
-   log metrics ([#&#8203;131](https://togithub.com/GoogleCloudPlatform/grpc-gcp-java/issues/131)).
-   map a key to current channel when bound call arrives but no mapping for the
    key exists ([#&#8203;132](https://togithub.com/GoogleCloudPlatform/grpc-gcp-java/issues/132)).
-   consolidate channel pool config in the GcpChannelPoolOptions ([#&#8203;109](https://togithub.com/GoogleCloudPlatform/grpc-gcp-java/issues/109)).

</details>

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first-party-dependencies/pom.xml

@@ -57,7 +57,7 @@
     <site.installationModule>${project.artifactId}</site.installationModule>
     <grpc.version>1.47.0</grpc.version>
     <gax.version>2.18.4</gax.version>
-    <grpc-gcp.version>1.1.0</grpc-gcp.version>
+    <grpc-gcp.version>1.2.1</grpc-gcp.version>
     <guava.version>31.1-jre</guava.version>
     <protobuf.version>3.21.2</protobuf.version>
     <google.api-common.version>2.2.1</google.api-common.version>