ready-to-merge label was not set when checks & reviews were green

[joestringer]

PR cilium/cilium#11375,

All CODEOWNERS reviews were satisfied and all checks were green except for GKE which is not required.

However the ready-to-merge label was not set. @christarazi added it manually.

[pchaigno]

Saw another occurrence of this bug at cilium/cilium#13323 (comment). All CIs were green, all codeowners were green, and there were 5 accept reviews + 1 comment review.