Update plugin com.diffplug.spotless to v8.9.0

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
com.diffplug.spotless	8.8.0 → 8.9.0

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Configuration

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

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[renovate]

⚠️ Artifact update problem

Renovate failed to update an artifact related to this branch. You probably do not want to merge this PR as-is.

♻ Renovate will retry this branch, including artifacts, only when one of the following happens:

• any of the package files in this branch needs updating, or
• the branch becomes conflicted, or
• you click the rebase/retry checkbox if found above, or
• you rename this PR's title to start with "rebase!" to trigger it manually

The artifact failure details are included below:

File name: library/build.gradle

Command failed: ./gradlew -Dorg.gradle.jvmargs=-Xms512m -Xmx512m --console=plain --dependency-verification lenient -q --write-verification-metadata sha256,pgp dependencies

FAILURE: Build completed with 2 failures.

1: Task failed with an exception.
-----------
* Where:
Script '/tmp/renovate/repos/github/nextcloud/android-library/jacoco.gradle' line: 31

* What went wrong:
A problem occurred configuring project ':library'.
> Could not create task ':library:testDebugUnitTest'.
   > Failed to calculate the value of task ':library:testDebugUnitTest' property 'javaLauncher'.
      > Cannot find a Java installation on your machine (Linux 6.1.155+ amd64) matching: {languageVersion=17, vendor=any vendor, implementation=vendor-specific, nativeImageCapable=false}. Toolchain download repositories have not been configured.

* Try:
> Learn more about toolchain auto-detection and auto-provisioning at https://docs.gradle.org/9.6.1/userguide/toolchains.html#sec:auto_detection.
> Learn more about toolchain repositories at https://docs.gradle.org/9.6.1/userguide/toolchains.html#sub:download_repositories.
> Run with --stacktrace option to get the stack trace.
> Run with --info or --debug option to get more log output.
> Run with --scan to get full insights from a Build Scan (powered by Develocity).
> Get more help at https://help.gradle.org.
==============================================================================

2: Task failed with an exception.
-----------
* Where:
Script '/tmp/renovate/repos/github/nextcloud/android-library/jacoco.gradle' line: 31

* What went wrong:
A problem occurred configuring project ':library'.
> Could not create task ':library:testDebugUnitTest'.
   > Failed to calculate the value of task ':library:testDebugUnitTest' property 'javaLauncher'.
      > Cannot find a Java installation on your machine (Linux 6.1.155+ amd64) matching: {languageVersion=17, vendor=any vendor, implementation=vendor-specific, nativeImageCapable=false}. Toolchain download repositories have not been configured.

* Try:
> Learn more about toolchain auto-detection and auto-provisioning at https://docs.gradle.org/9.6.1/userguide/toolchains.html#sec:auto_detection.
> Learn more about toolchain repositories at https://docs.gradle.org/9.6.1/userguide/toolchains.html#sub:download_repositories.
> Run with --stacktrace option to get the stack trace.
> Run with --info or --debug option to get more log output.
> Run with --scan to get full insights from a Build Scan (powered by Develocity).
> Get more help at https://help.gradle.org.
==============================================================================

BUILD FAILED in 1m 34s