Update deps fails to update vendorless project

[cardil]

As seen in this build https://github.com/knative-extensions/knobots/actions/runs/6490025840/job/17625229242, the update-deps bot fails to update the vendorless project dependencies. See: knative/func#1964

/kind bug

The following code block doesn't open PR if there are only changes to go.mod or go.sum. Definitely, that's invalid in vendorless case.

knobots/actions/update-deps/entrypoint.sh

Lines 75 to 78 in f15f57f

	if [ "$(basename $x)" = "go.mod" ]; then
	continue
	elif [ "$(basename $x)" = "go.sum" ]; then
	continue

[cardil]

/assign