l10n tooling: remove the fallback mechanism

The hippo-cms-l10n-maven-plugin has a fallback mechanism to include l10n jars of a lower micro version.

It's a one-off in the build system and causes problems and questions for customers.

• warnings "Could not resolve artifact"
• lengthy build process because Maven proxy tries to download many unavailable artifacts

Please consider using regular Maven dependencies (e.g. deploying all l10n artifacts under all micro versions).