deps: update dependency com.google.cloud:google-cloud-core to v2.8.20 (googleapis#852)

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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) | `2.8.19` -> `2.8.20` | [![age](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.20/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.20/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.20/compatibility-slim/2.8.19)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-core/2.8.20/confidence-slim/2.8.19)](https://docs.renovatebot.com/merge-confidence/) |

---

### Release Notes

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

### [`v2.8.20`](https://togithub.com/googleapis/java-core/blob/HEAD/CHANGELOG.md#&#8203;2820-httpsgithubcomgoogleapisjava-corecomparev2819v2820-2022-10-02)

[Compare Source](https://togithub.com/googleapis/java-core/compare/v2.8.19...v2.8.20)

##### Dependencies

-   Update dependency com.google.api:gax-bom to v2.19.2 ([#&googleapis#8203;969](https://togithub.com/googleapis/java-core/issues/969)) ([1151449](https://togithub.com/googleapis/java-core/commit/1151449c061ab51c45982444db5f9da9d2ce4fb7))
-   Update dependency com.google.api.grpc:proto-google-common-protos to v2.9.6 ([#&googleapis#8203;967](https://togithub.com/googleapis/java-core/issues/967)) ([4a7b524](https://togithub.com/googleapis/java-core/commit/4a7b524fa366484825bedbc0a4f86d4551a6a0e8))
-   Update dependency io.grpc:grpc-bom to v1.49.2 ([#&googleapis#8203;966](https://togithub.com/googleapis/java-core/issues/966)) ([b7738aa](https://togithub.com/googleapis/java-core/commit/b7738aa71fb9cf0994e4ad1dae4bae433754cda0))

</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>2.8.19</version>
+      <version>2.8.20</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>2.8.19</version>
+      <version>2.8.20</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>2.8.19</version>
+      <version>2.8.20</version>
       <classifier>tests</classifier>
     </dependency>
   </dependencies>