chore: Remove `GCPLoadBalancerImbalancedBackends` alert
What
Remove GCPLoadBalancerImbalancedBackends
alert.
Why
This was removed after discussion in on-call handover meeting due to its insignificance and lack of clarity by this MR but it was readded (unintentionally) during a wider renaming MR here.
Reference: !7452 (merged)