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.*}

Comienza con la configuración de compilación de Maven que invoca com.diffplug.spotless:spotless-maven-plugin:2.30.0 y define la versión de Scala. Ejecuta la compilación de Maven para reproducir el error de JCTree y, a continuación, verifica que las actualizaciones solicitadas de Spotless y Scala permiten que la compilación se complete correctamente; el issue ya enlaza PR #1287.

Escrito por el modelo de indexación a partir del texto del issue.