deps: update dependency com.google.cloud:google-cloud-core to v2.8.12 (#940)

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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) | `2.8.11` -> `2.8.12` | [![age](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.12/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.12/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.12/compatibility-slim/2.8.11)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.12/confidence-slim/2.8.11)](https://docs.renovatebot.com/merge-confidence/) |

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### Release Notes

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

### [`v2.8.12`](https://togithub.com/googleapis/java-core/blob/HEAD/CHANGELOG.md#&#8203;2812-httpsgithubcomgoogleapisjava-corecomparev2811v2812-2022-09-14)

[Compare Source](https://togithub.com/googleapis/java-core/compare/v2.8.11...v2.8.12)

##### Dependencies

-   Update dependency com.google.api:gax-bom to v2.19.1 ([#&#8203;915](https://togithub.com/googleapis/java-core/issues/915)) ([2647fde](https://togithub.com/googleapis/java-core/commit/2647fdee8e2b168f3364af8e76abfe2903578b29))
-   Update dependency com.google.protobuf:protobuf-bom to v3.21.6 ([#&#8203;916](https://togithub.com/googleapis/java-core/issues/916)) ([a7db234](https://togithub.com/googleapis/java-core/commit/a7db234800481ffba71d3222542971dbcd212d8e))

</details>

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Author: renovate-bot

samples/install-without-bom/pom.xml

@@ -36,7 +36,7 @@
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-core</artifactId>
-      <version>2.8.11</version>
+      <version>2.8.12</version>
     </dependency>
     <dependency>
       <groupId>junit</groupId>

samples/snapshot/pom.xml

@@ -35,7 +35,7 @@
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-core</artifactId>
-      <version>2.8.11</version>
+      <version>2.8.12</version>
     </dependency>
     <dependency>
       <groupId>junit</groupId>