contributors/devel: Remove oncall reference (deprecated) from README.md
contributors/devel: Remove oncall reference (deprecated) from README.md

- Deprecated by: kubernetes/community@fc975ed59114079b3a3789fed4c2d3aac0b3cda3

kubernetes/community,kubernetes/community,kubernetes/community,bgrant0607/community,pwittrock/community,bgrant0607/community,pwittrock/community