deps: update dependency com.google.cloud:google-cloud-core to v2.8.6 (#911)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [com.google.cloud:google-cloud-core](https://github.com/googleapis/java-core) | `2.8.5` -> `2.8.6` | [![age](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.6/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.6/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.6/compatibility-slim/2.8.5)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.6/confidence-slim/2.8.5)](https://docs.renovatebot.com/merge-confidence/) |

---

### Release Notes

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

### [`v2.8.6`](https://github.com/googleapis/java-core/blob/HEAD/CHANGELOG.md#&#8203;286-httpsgithubcomgoogleapisjava-corecomparev285v286-2022-08-02)

[Compare Source](https://github.com/googleapis/java-core/compare/v2.8.5...v2.8.6)

##### Dependencies

-   update dependency com.google.api:gax-bom to v2.18.7 ([#&#8203;890](https://github.com/googleapis/java-core/issues/890)) ([c67bed5](https://github.com/googleapis/java-core/commit/c67bed5281b458e78780cdd918235b5d073917c7))
-   update dependency com.google.code.gson:gson to v2.9.1 ([#&#8203;888](https://github.com/googleapis/java-core/issues/888)) ([7b799c6](https://github.com/googleapis/java-core/commit/7b799c66f4aaf057242e9a231b920e49a7c964e9))

</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>2.8.5</version>
+      <version>2.8.6</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>2.8.5</version>
+      <version>2.8.6</version>
     </dependency>
     <dependency>
       <groupId>junit</groupId>