Fixed broken link in contributing doc

[varunpatel07]

Fixes #3210

[rkpattnaik780]

Thanks a lot for the fix @varunpatel07.
To get the DCO check passing you need to signoff your commit. You can follow these steps:

1. git commit --amend --no-edit --signoff
2. git push origin main -f

[romeokienzler]

@varunpatel07 can you please sign off the DCO? you can also join the community call Friday 8:30 AM PST or ask on Slack if you need help elyra-ai.slack.com / https://ibm.webex.com/meet/romeo.kienzler1