Bug#978933: node-rollup-plugin-babel: drop legacy plugin for bullseye

[Pirate Praveen]

Package: node-rollup-plugin-babel
Version: 5.2.1+repack+~4.4.0-2
Severity: important
I think we should try to remove the embedded copy of legacy plugin to 
reduce maintenance for bullseye (similar to how we did node-resolve 
plugin).