deps: update dependency com.google.cloud:google-cloud-core to v2.8.1 (#761)

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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) | `2.8.0` -> `2.8.1` | [![age](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.1/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.1/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.1/compatibility-slim/2.8.0)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.1/confidence-slim/2.8.0)](https://docs.renovatebot.com/merge-confidence/) |

---

### Release Notes

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

### [`v2.8.1`](https://togithub.com/googleapis/java-core/blob/HEAD/CHANGELOG.md#&#8203;281-httpsgithubcomgoogleapisjava-corecomparev280v281-2022-06-27)

[Compare Source](https://togithub.com/googleapis/java-core/compare/v2.8.0...v2.8.1)

##### Dependencies

-   update dependency com.google.protobuf:protobuf-bom to v3.21.2 ([#&#8203;851](https://togithub.com/googleapis/java-core/issues/851)) ([c0f09f0](https://togithub.com/googleapis/java-core/commit/c0f09f0fcd57a2d90e0a99b17c9e346df8651d65))

</details>

---

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Author: renovate-bot

java-accessapproval/samples/install-without-bom/pom.xml

@@ -48,7 +48,7 @@
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-core</artifactId>
-      <version>2.8.0</version>
+      <version>2.8.1</version>
       <classifier>tests</classifier>
     </dependency>
   </dependencies>

java-accessapproval/samples/snapshot/pom.xml

@@ -46,7 +46,7 @@
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-core</artifactId>
-      <version>2.8.0</version>
+      <version>2.8.1</version>
       <classifier>tests</classifier>
     </dependency>
   </dependencies>

java-accessapproval/samples/snippets/pom.xml

@@ -59,7 +59,7 @@
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-core</artifactId>
-      <version>2.8.0</version>
+      <version>2.8.1</version>
       <classifier>tests</classifier>
     </dependency>
   </dependencies>