deps: update google.core.version to v2.8.20 (#848)

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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) | `2.8.19` -> `2.8.20` | [![age](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.20/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.20/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.20/compatibility-slim/2.8.19)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.20/confidence-slim/2.8.19)](https://docs.renovatebot.com/merge-confidence/) |
| [com.google.cloud:google-cloud-core-bom](https://togithub.com/googleapis/java-core) | `2.8.19` -> `2.8.20` | [![age](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core-bom/2.8.20/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core-bom/2.8.20/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core-bom/2.8.20/compatibility-slim/2.8.19)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core-bom/2.8.20/confidence-slim/2.8.19)](https://docs.renovatebot.com/merge-confidence/) |

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### Release Notes

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

### [`v2.8.20`](https://togithub.com/googleapis/java-core/blob/HEAD/CHANGELOG.md#&#8203;2820-httpsgithubcomgoogleapisjava-corecomparev2819v2820-2022-10-02)

[Compare Source](https://togithub.com/googleapis/java-core/compare/v2.8.19...v2.8.20)

##### Dependencies

-   Update dependency com.google.api:gax-bom to v2.19.2 ([#&#8203;969](https://togithub.com/googleapis/java-core/issues/969)) ([1151449](https://togithub.com/googleapis/java-core/commit/1151449c061ab51c45982444db5f9da9d2ce4fb7))
-   Update dependency com.google.api.grpc:proto-google-common-protos to v2.9.6 ([#&#8203;967](https://togithub.com/googleapis/java-core/issues/967)) ([4a7b524](https://togithub.com/googleapis/java-core/commit/4a7b524fa366484825bedbc0a4f86d4551a6a0e8))
-   Update dependency io.grpc:grpc-bom to v1.49.2 ([#&#8203;966](https://togithub.com/googleapis/java-core/issues/966)) ([b7738aa](https://togithub.com/googleapis/java-core/commit/b7738aa71fb9cf0994e4ad1dae4bae433754cda0))

</details>

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java-shared-dependencies/first-party-dependencies/pom.xml

@@ -63,7 +63,7 @@
     <protobuf.version>3.21.7</protobuf.version>
     <google.api-common.version>2.2.1</google.api-common.version>
     <google.common-protos.version>2.9.6</google.common-protos.version>
-    <google.core.version>2.8.19</google.core.version>
+    <google.core.version>2.8.20</google.core.version>
     <google.auth.version>1.11.0</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>