chore: build tag consistency (#654)

The integration tests and unit tests are currently expected to be
disjunct sets.  While we may change to being additive in the future,
this change makes us consistent by adding the integration exclusion tag
to a few non-integration test files where it was currently missing.

cloudevents/emitter_test.go

@@ -1,3 +1,6 @@
+//go:build !integration
+// +build !integration
+
 package cloudevents
 
 import (

docker/credentials_helper_test.go

@@ -1,3 +1,6 @@
+//go:build !integration
+// +build !integration
+
 package docker
 
 import "testing"

docker/pusher_test.go

@@ -1,3 +1,6 @@
+//go:build !integration
+// +build !integration
+
 package docker
 
 import (

knative/deployer_test.go

@@ -1,3 +1,6 @@
+//go:build !integration
+// +build !integration
+
 package knative
 
 import (

repository_test.go

@@ -1,3 +1,6 @@
+//go:build !integration
+// +build !integration
+
 package function_test
 
 import (