test(deps): update dependency org.mockito:mockito-core to v4.7.0 (#1974)

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

This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [org.mockito:mockito-core](https://togithub.com/mockito/mockito) | `4.6.1` -> `4.7.0` | [![age](https://badges.renovateapi.com/packages/maven/org.mockito:mockito-core/4.7.0/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/org.mockito:mockito-core/4.7.0/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/org.mockito:mockito-core/4.7.0/compatibility-slim/4.6.1)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/org.mockito:mockito-core/4.7.0/confidence-slim/4.6.1)](https://docs.renovatebot.com/merge-confidence/) |

---

### 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**: Renovate will not automatically rebase this PR, because other commits have been found.

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

---

 - [ ] <!-- rebase-check -->If you want to rebase/retry this PR, click this checkbox. ⚠ **Warning**: custom changes will be lost.

---

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).
<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiIzMi4xNTguMCIsInVwZGF0ZWRJblZlciI6IjMyLjE1OC4wIn0=-->

README.md

@@ -49,7 +49,7 @@ If you are using Maven without BOM, add this to your dependencies:
 If you are using Gradle 5.x or later, add this to your dependencies:
 
 ```Groovy
-implementation platform('com.google.cloud:libraries-bom:26.0.0')
+implementation platform('com.google.cloud:libraries-bom:26.1.0')
 
 implementation 'com.google.cloud:google-cloud-spanner'
 ```

google-cloud-spanner/pom.xml

@@ -338,7 +338,7 @@
     <dependency>
       <groupId>org.mockito</groupId>
       <artifactId>mockito-core</artifactId>
-      <version>4.6.1</version>
+      <version>4.7.0</version>
       <scope>test</scope>
     </dependency>
     <dependency>