Upgrade Spotless to 0.43.0 & Scala 2.12.19

Currently building off of master is broken because of:

```

[ERROR] Failed to execute goal com.diffplug.spotless:spotless-maven-plugin:2.30.0:check (default) on project parquet-format-structures: Execution default of goal com.diffplug.spotless:spotless-maven-plugin:2.30.0:check failed: java.lang.reflect.InvocationTargetException: 'com.sun.tools.javac.tree.JCTree com.sun.tools.javac.tree.JCTree$JCImport.getQualifiedIdentifier()' -> [Help 1]

```

Arrow hit the same issue: because of this: Bumping spotless to fix building on master.

**Reporter**: [Vinoo Ganesh](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=vinooganesh) / @vinooganesh
**Assignee**: [Vinoo Ganesh](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=vinooganesh) / @vinooganesh
#### PRs and other links:
- [GitHub Pull Request #1287](https://github.com/apache/parquet-mr/pull/1287)

_{**Note**: *This issue was originally created as [PARQUET-2441](https://issues.apache.org/jira/browse/PARQUET-2441). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}

Beginnen Sie mit der Maven-Build-Konfiguration, die com.diffplug.spotless:spotless-maven-plugin:2.30.0 aufruft und die Scala-Version definiert. Führen Sie den Maven-Build aus, um den JCTree-Fehler zu reproduzieren, und überprüfen Sie anschließend, dass die angeforderten Spotless- und Scala-Upgrades den Build erfolgreich abschließen lassen; das Issue verlinkt bereits PR #1287.

Vom Indexierungsmodell aus dem Issue-Text verfasst.