deps: update dependency com.google.cloud:google-cloud-core to v2.8.4 (#907)

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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) | `2.8.3` -> `2.8.4` | [![age](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.4/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.4/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.4/compatibility-slim/2.8.3)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.4/confidence-slim/2.8.3)](https://docs.renovatebot.com/merge-confidence/) |

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### Release Notes

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

### [`v2.8.4`](https://togithub.com/googleapis/java-core/blob/HEAD/CHANGELOG.md#&#8203;284-httpsgithubcomgoogleapisjava-corecomparev283v284-2022-07-27)

[Compare Source](https://togithub.com/googleapis/java-core/compare/v2.8.3...v2.8.4)

##### Documentation

-   update javadocs for ReadChannel#limit to be more clear ([#&#8203;880](https://togithub.com/googleapis/java-core/issues/880)) ([c7de4e2](https://togithub.com/googleapis/java-core/commit/c7de4e2871d6a32cacc7aab69d826f3afd6301ef))

##### Dependencies

-   Update google-cloud-shared-config to v1.5.3 ([#&#8203;882](https://togithub.com/googleapis/java-core/issues/882)) ([aabb0b4](https://togithub.com/googleapis/java-core/commit/aabb0b42076f8a02e7b31d604add567fa909df6c))

</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>2.8.3</version>
+      <version>2.8.4</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>2.8.3</version>
+      <version>2.8.4</version>
     </dependency>
     <dependency>
       <groupId>junit</groupId>