deps: update dependency com.google.cloud:google-cloud-kms-bom to v2.6.0 (#4661)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [com.google.cloud:google-cloud-kms-bom](https://togithub.com/googleapis/java-kms) | `2.5.3` -> `2.6.0` | [![age](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-kms-bom/2.6.0/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-kms-bom/2.6.0/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-kms-bom/2.6.0/compatibility-slim/2.5.3)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-kms-bom/2.6.0/confidence-slim/2.5.3)](https://docs.renovatebot.com/merge-confidence/) |

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### Release Notes

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

### [`v2.6.0`](https://togithub.com/googleapis/java-kms/blob/HEAD/CHANGELOG.md#&#8203;260-httpsgithubcomgoogleapisjava-kmscomparev253v260-2022-07-01)

[Compare Source](https://togithub.com/googleapis/java-kms/compare/v2.5.3...v2.6.0)

##### Features

-   Enable REST transport for most of Java and Go clients ([#&#8203;801](https://togithub.com/googleapis/java-kms/issues/801)) ([64f351e](https://togithub.com/googleapis/java-kms/commit/64f351e96901c359723a7df610dd329cf75ed89c))

##### Bug Fixes

-   update gapic-generator-java with mock service generation fixes ([#&#8203;809](https://togithub.com/googleapis/java-kms/issues/809)) ([8cb34ce](https://togithub.com/googleapis/java-kms/commit/8cb34cec429b48ed95e0a73a89ba978d2995a778))

##### Dependencies

-   update dependency com.google.protobuf:protobuf-java-util to v3.21.2 ([#&#8203;807](https://togithub.com/googleapis/java-kms/issues/807)) ([be24089](https://togithub.com/googleapis/java-kms/commit/be24089f54fb7c2084d97c208d64fc75f810ae25))

</details>

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Author: renovate-bot

google-cloud-bom/pom.xml

@@ -505,7 +505,7 @@
       <dependency>
         <groupId>com.google.cloud</groupId>
         <artifactId>google-cloud-kms-bom</artifactId>
-        <version>2.5.3</version>
+        <version>2.6.0</version>
         <type>pom</type>
         <scope>import</scope>
       </dependency>