CONTRIBUTING: update help wanted issues label (#7515)
CONTRIBUTING: update help wanted issues label (#7515)

Signed-off-by: Rohan Jain <f3a935f2cb7c3d75d1446a19169b923809d6e623@gmail.com>
BusyJay/tikv,BusyJay/tikv,BusyJay/tikv,c4pt0r/tikv,pingcap/tikv,BusyJay/tikv,pingcap/tikv