chore(deps): update plugin com.diffplug.eclipse.apt to v3.37.2 (#1771)

[![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.diffplug.eclipse.apt | `3.37.1` -> `3.37.2` | [![age](https://badges.renovateapi.com/packages/maven/com.diffplug.eclipse.apt/3.37.2/age-slim)](https://docs.renovatebot.com/merge-confidence/) | [![adoption](https://badges.renovateapi.com/packages/maven/com.diffplug.eclipse.apt/3.37.2/adoption-slim)](https://docs.renovatebot.com/merge-confidence/) | [![passing](https://badges.renovateapi.com/packages/maven/com.diffplug.eclipse.apt/3.37.2/compatibility-slim/3.37.1)](https://docs.renovatebot.com/merge-confidence/) | [![confidence](https://badges.renovateapi.com/packages/maven/com.diffplug.eclipse.apt/3.37.2/confidence-slim/3.37.1)](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**: 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, click this checkbox.

---

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/gax-java).
<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiIzMi4xNTMuMCIsInVwZGF0ZWRJblZlciI6IjMyLjE1My4wIn0=-->

build.gradle

@@ -4,7 +4,7 @@ plugins {
   id 'java'
   id 'io.github.gradle-nexus.publish-plugin' version '1.1.0'
 
-  id 'com.diffplug.eclipse.apt' version '3.37.1' apply false
+  id 'com.diffplug.eclipse.apt' version '3.37.2' apply false
   id 'com.dorongold.task-tree' version '2.1.0' apply false
   id 'com.github.johnrengelman.shadow' version '7.1.2' apply false
   id 'com.github.sherter.google-java-format' version '0.9' apply false