feat!: Don't ping Ned (#314)

Ned isn't working at 2U anymore, so we should not be bothering him!

I'm not replacing this with better contact info, as it's not clear who that would be—or whether we even want this no-contributions behavior at all. So in the meantime, just removing incorrect info.

openedx_webhooks/templates/no_contributions.md.j2

@@ -1,6 +1,5 @@
 {% filter replace("\n", " ")|trim %}
 Thanks for your pull request, but this repo does not accept outside contributions unless they are under contract.
-If you think this is an error, please contact @nedbat.
 {% endfilter %}
 
 <!-- comment:no-contributions -->