[releng] 1.20: Add 1.22 and remove 1.18 milestone_applier rules
[releng] 1.20: Add 1.22 and remove 1.18 milestone_applier rules

This commit adds the 1.22 branch configuration and removes the 1.18
rule for the milestone_applier plugin.

Signed-off-by: Adolfo García Veytia (Puerco) <9de42c8261a7cacaae239656a4dd6991d9b9250f@uservers.net>

fejta/test-infra,BenTheElder/test-infra,cjwagner/test-infra,jessfraz/test-infra,BenTheElder/test-infra,BenTheElder/test-infra,jessfraz/test-infra,michelle192837/test-infra,michelle192837/test-infra,monopole/test-infra,monopole/test-infra,fejta/test-infra,kubernetes/test-infra,michelle192837/test-infra,fejta/test-infra,BenTheElder/test-infra,michelle192837/test-infra,cblecker/test-infra,kubernetes/test-infra,fejta/test-infra,dims/test-infra,kubernetes/test-infra,cjwagner/test-infra,cjwagner/test-infra,jessfraz/test-infra,michelle192837/test-infra,kubernetes/test-infra,cblecker/test-infra,jessfraz/test-infra,BenTheElder/test-infra,kubernetes/test-infra,monopole/test-infra,dims/test-infra,monopole/test-infra,kubernetes/test-infra,cblecker/test-infra,dims/test-infra,dims/test-infra,jessfraz/test-infra,cjwagner/test-infra,michelle192837/test-infra,cblecker/test-infra,cblecker/test-infra,dims/test-infra,fejta/test-infra,BenTheElder/test-infra,monopole/test-infra,fejta/test-infra,cjwagner/test-infra,jessfraz/test-infra,monopole/test-infra,dims/test-infra,cblecker/test-infra,cjwagner/test-infra