Cleanup metallb unnecesary things after Sylva 1.2+

The following discussion from !3101 (merged) should be addressed:

• @tmmorin started a discussion: (+3 comments)

  also, it would be good to:

  • add a comment to indicate that this can be removed after 1.2 release
  • track an issue to not forget this cleanup
  • (and the removal of metallb-chart-cleanup as well)
  • and the removal of the policy added by !3234 (merged) 😄