e2e tests are run against an old version of eventing-sources

[bbrowning]

Expected Behavior

e2e tests on master branch run against the latest eventing-sources release

Actual Behavior

e2e tests on master branch run against a pinned event-sources release from early december

[n3wscott]

/assign

[vaikas]

@n3wscott this can now be closed? reopen if not.