deps: update dependency com.google.cloud:google-cloud-core to v2.8.18 (#1274)

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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) | `2.8.17` -> `2.8.18` | [![age](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.18/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.18/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.18/compatibility-slim/2.8.17)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.18/confidence-slim/2.8.17)](https://docs.renovatebot.com/merge-confidence/) |

---

### Release Notes

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

### [`v2.8.18`](https://togithub.com/googleapis/java-core/blob/HEAD/CHANGELOG.md#&#8203;2818-httpsgithubcomgoogleapisjava-corecomparev2817v2818-2022-09-30)

[Compare Source](https://togithub.com/googleapis/java-core/compare/v2.8.17...v2.8.18)

##### Dependencies

-   Update dependency com.google.protobuf:protobuf-bom to v3.21.7 ([#&#8203;960](https://togithub.com/googleapis/java-core/issues/960)) ([1fcd95f](https://togithub.com/googleapis/java-core/commit/1fcd95f2401b66a79383bd79729595334493b0e4))

</details>

---

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Author: renovate-bot

samples/install-without-bom/pom.xml

@@ -63,7 +63,7 @@
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-core</artifactId>
-      <version>2.8.17</version>
+      <version>2.8.18</version>
       <scope>test</scope>
       <classifier>tests</classifier>
     </dependency>

samples/snapshot/pom.xml

@@ -62,7 +62,7 @@
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-core</artifactId>
-      <version>2.8.17</version>
+      <version>2.8.18</version>
       <scope>test</scope>
       <classifier>tests</classifier>
     </dependency>

samples/snippets/pom.xml

@@ -71,7 +71,7 @@
     <dependency>
       <groupId>com.google.cloud</groupId>
       <artifactId>google-cloud-core</artifactId>
-      <version>2.8.17</version>
+      <version>2.8.18</version>
       <scope>test</scope>
       <classifier>tests</classifier>
     </dependency>