Bump com.diffplug.spotless:spotless-plugin-gradle in /codegen (#576)

Bumps [com.diffplug.spotless:spotless-plugin-gradle](https://github.com/diffplug/spotless) from 7.2.1 to 8.0.0.
- [Release notes](https://github.com/diffplug/spotless/releases)
- [Changelog](https://github.com/diffplug/spotless/blob/main/CHANGES.md)
- [Commits](diffplug/spotless@gradle/7.2.1...gradle/8.0.0)

---
updated-dependencies:
- dependency-name: com.diffplug.spotless:spotless-plugin-gradle
  dependency-version: 8.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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Author: dependabot[bot]

codegen/gradle/libs.versions.toml

@@ -3,7 +3,7 @@ junit5 = "5.13.4"
 smithy = "1.62.0"
 test-logger-plugin = "4.0.0"
 spotbugs = "6.0.22"
-spotless = "7.2.1"
+spotless = "8.0.0"
 smithy-gradle-plugins = "1.3.0"
 dep-analysis = "3.1.0"
 jsoup = "1.21.2"