Update deprecated annotations for Metallb 0.14.9

Following merge of Metallb 0.14.9 (!3506 (merged) and discussion !3506 (comment 2266952972)), and as mentionned on associated release note :

The annotation prefix "metallb.universe.tf" is deprecated by now. Please use the new prefix "metallb.io". E.g.  "metallb.io/address-pool"
instead of "metallb.universe.tf/address-pool". The old prefix is still supported. However, migrating to the new prefix is highly recommend. 
Future versions might remove this backwards compatibility. (#2495, @disco-stu)

We need to replace annotations metallb.universe.tf by metallb.io.