fix(deps): update dependency com.google.appengine:appengine-api-1.0-sdk to v2.0.15 (#2327)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [com.google.appengine:appengine-api-1.0-sdk](https://togithub.com/GoogleCloudPlatform/appengine-java-standard) | `2.0.14` -> `2.0.15` | [![age](https://badges.renovateapi.com/packages/maven/com.google.appengine:appengine-api-1.0-sdk/2.0.15/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.google.appengine:appengine-api-1.0-sdk/2.0.15/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.google.appengine:appengine-api-1.0-sdk/2.0.15/compatibility-slim/2.0.14)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.google.appengine:appengine-api-1.0-sdk/2.0.15/confidence-slim/2.0.14)](https://docs.renovatebot.com/merge-confidence/) |

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### ⚠ Dependency Lookup Warnings ⚠

Warnings were logged while processing this repo. Please check the Dependency Dashboard for more information.

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### Release Notes

<details>
<summary>GoogleCloudPlatform/appengine-java-standard</summary>

### [`v2.0.15`](https://togithub.com/GoogleCloudPlatform/appengine-java-standard/releases/tag/v2.0.15)

[Compare Source](https://togithub.com/GoogleCloudPlatform/appengine-java-standard/compare/v2.0.14...v2.0.15)

**Full Changelog**: https://togithub.com/GoogleCloudPlatform/appengine-java-standard/compare/v2.0.14...v2.0.15

</details>

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Author: renovate-bot

pom.xml

@@ -503,7 +503,7 @@
     <project.gson.version>2.8.6</project.gson.version>
     <project.protobuf-java.version>3.23.2</project.protobuf-java.version>
     <project.guava.version>32.0.0-jre</project.guava.version>
-    <project.appengine.version>2.0.14</project.appengine.version>
+    <project.appengine.version>2.0.15</project.appengine.version>
     <project.xpp3.version>1.1.4c</project.xpp3.version>
     <project.jdo2-api.version>2.3-20090302111651</project.jdo2-api.version>
     <project.datanucleus-core.version>3.2.2</project.datanucleus-core.version>