Merge pull request #1501 from k8s-infra-cherrypick-robot/cherry-pick-1493-to-release-1.9

[release-1.9] add songjiaxun to owners

Author: tyuchn

OWNERS

@@ -6,6 +6,7 @@ reviewers:
   - saikat-royc
   - pwschuurman
   - tyuchn
+  - songjiaxun
 approvers:
   - amacaskill
   - leiyiz
@@ -14,6 +15,7 @@ approvers:
   - saikat-royc
   - pwschuurman
   - tyuchn
+  - songjiaxun
 emeritus_reviewers:
   - davidz627
   - jingxu97