Update CONTRIBUTING.md

[spron-in]

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[JNKPercona]

Test name	Status
recreate	passed
haproxy	passed
storage	passed
upgrade-haproxy	passed
scaling	passed
big-data	passed
scheduled-backup	passed
self-healing	passed
scaling-proxysql	passed
init-deploy	passed
restore-to-encrypted-cluster	passed
security-context	passed
upgrade-proxysql	passed
limits	passed
self-healing-chaos	failed
smart-update	passed
demand-backup	passed
monitoring-2-0	passed
self-healing-advanced	passed
affinity	passed
one-pod	passed
self-healing-advanced-chaos	failed
operator-self-healing	passed
auto-tuning	passed
proxysql-sidecar-res-limits	passed
operator-self-healing-chaos	failed
pitr	passed
users	passed
upgrade-consistency	passed
demand-backup-encrypted-with-tls	failed
tls-issue-self	passed
tls-issue-cert-manager	passed
tls-issue-cert-manager-ref	passed
validation-hook	failed

commit: ef0b90c
image: perconalab/percona-xtradb-cluster-operator:PR-898-ef0b90cc