chore: fix build and test tags (knative#2911)

The current build tagging system was predicated on the idea that
integraion, e2e and unit tests are entirely separate.  The correct way
to treat these is as inclusive with unit tests.  Thus this pr removes
the exclusion of unit test from integration tests runs, treating -tags
integration as indicating "unit tests plus integration tests".

Author: lkingland

pkg/docker/creds/credentials_test.go

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

pkg/docker/pusher_test.go

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

pkg/docker/runner_test.go

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

pkg/functions/client_test.go

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

pkg/functions/config_test.go

@@ -1,6 +1,3 @@
-//go:build !integration
-// +build !integration
-
 package functions_test
 
 // Config tests do not have private access, as they are testing manifest

pkg/functions/function_envs_unit_test.go

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

pkg/functions/function_git_unit_test.go

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

pkg/functions/function_labels_unit_test.go

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

pkg/functions/function_migrations_unit_test.go

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

pkg/functions/function_options_unit_test.go

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