deps: update google.core.version to v2.8.7 (#774)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [com.google.cloud:google-cloud-core](https://togithub.com/googleapis/java-core) | `2.8.6` -> `2.8.7` | [![age](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.7/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.7/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.7/compatibility-slim/2.8.6)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.7/confidence-slim/2.8.6)](https://docs.renovatebot.com/merge-confidence/) |
| [com.google.cloud:google-cloud-core-bom](https://togithub.com/googleapis/java-core) | `2.8.6` -> `2.8.7` | [![age](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core-bom/2.8.7/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core-bom/2.8.7/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core-bom/2.8.7/compatibility-slim/2.8.6)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core-bom/2.8.7/confidence-slim/2.8.6)](https://docs.renovatebot.com/merge-confidence/) |

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### Release Notes

<details>
<summary>googleapis/java-core</summary>

### [`v2.8.7`](https://togithub.com/googleapis/java-core/blob/HEAD/CHANGELOG.md#&#8203;287-httpsgithubcomgoogleapisjava-corecomparev286v287-2022-08-03)

[Compare Source](https://togithub.com/googleapis/java-core/compare/v2.8.6...v2.8.7)

##### Dependencies

-   update dependency com.google.auth:google-auth-library-bom to v1.9.0 ([#&#8203;894](https://togithub.com/googleapis/java-core/issues/894)) ([82aaa16](https://togithub.com/googleapis/java-core/commit/82aaa16cd9813984a0c92d944eb1ad956759a8e5))
-   update dependency io.grpc:grpc-bom to v1.48.1 ([#&#8203;891](https://togithub.com/googleapis/java-core/issues/891)) ([0b0f9b8](https://togithub.com/googleapis/java-core/commit/0b0f9b89757b801e8334c764644d7b66032d36d1))

</details>

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first-party-dependencies/pom.xml

@@ -62,7 +62,7 @@
     <protobuf.version>3.21.4</protobuf.version>
     <google.api-common.version>2.2.1</google.api-common.version>
     <google.common-protos.version>2.9.2</google.common-protos.version>
-    <google.core.version>2.8.6</google.core.version>
+    <google.core.version>2.8.7</google.core.version>
     <google.auth.version>1.9.0</google.auth.version>
     <google.http-client.version>1.42.2</google.http-client.version>
     <google.oauth-client.version>1.34.1</google.oauth-client.version>