deps: update dependency com.google.cloud:google-cloud-spanner-bom to v6.43.0 (#1255)

[![Mend Renovate](https://app.renovatebot.com/images/banner.svg)](https://renovatebot.com)

This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [com.google.cloud:google-cloud-spanner-bom](https://togithub.com/googleapis/java-spanner) | `6.42.3` -> `6.43.0` | [![age](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-spanner-bom/6.43.0/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-spanner-bom/6.43.0/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-spanner-bom/6.43.0/compatibility-slim/6.42.3)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.cloud:google-cloud-spanner-bom/6.43.0/confidence-slim/6.42.3)](https://docs.renovatebot.com/merge-confidence/) |

---

### Release Notes

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

### [`v6.43.0`](https://togithub.com/googleapis/java-spanner/blob/HEAD/CHANGELOG.md#&#8203;6430-httpsgithubcomgoogleapisjava-spannercomparev6423v6430-2023-06-07)

[Compare Source](https://togithub.com/googleapis/java-spanner/compare/v6.42.3...v6.43.0)

##### Features

-   Delay transaction start option ([#&#8203;2462](https://togithub.com/googleapis/java-spanner/issues/2462)) ([f1cbd16](https://togithub.com/googleapis/java-spanner/commit/f1cbd168a7e5f48206cdfc2d782835cf7ccb8b0d))
-   Make administrative request retries optional ([#&#8203;2476](https://togithub.com/googleapis/java-spanner/issues/2476)) ([ee6548c](https://togithub.com/googleapis/java-spanner/commit/ee6548cfa511d6efc99f508290ed0b1ce025a4cc))

##### Dependencies

-   Update dependency com.google.cloud:google-cloud-shared-dependencies to v3.11.0 ([#&#8203;2486](https://togithub.com/googleapis/java-spanner/issues/2486)) ([82400d5](https://togithub.com/googleapis/java-spanner/commit/82400d5576c3ffe08ff6bb94d8b1a307e2f41662))

</details>

---

### Configuration

📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined).

🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update again.

---

 - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check this box

---

This PR has been generated by [Mend Renovate](https://www.mend.io/free-developer-tools/renovate/). View repository job log [here](https://app.renovatebot.com/dashboard#github/googleapis/java-spanner-jdbc).
<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiIzNS4xMTAuMCIsInVwZGF0ZWRJblZlciI6IjM1LjExMC4wIiwidGFyZ2V0QnJhbmNoIjoibWFpbiJ9-->

Author: renovate-bot

pom.xml

@@ -62,7 +62,7 @@
       <dependency>
         <groupId>com.google.cloud</groupId>
         <artifactId>google-cloud-spanner-bom</artifactId>
-        <version>6.42.3</version>
+        <version>6.43.0</version>
         <type>pom</type>
         <scope>import</scope>
       </dependency>