Remove old build tag comments

Go is transitioning from the old '// +build' form to '//go:build', this
removes all uses of the old form, adding the new one where needed.

See https://go.googlesource.com/proposal/+/master/design/draft-gobuild.md

cmd/osbuild-auth-tests/certificates.go

@@ -1,5 +1,4 @@
 //go:build integration
-// +build integration
 
 package main
 

cmd/osbuild-auth-tests/main_test.go

@@ -1,5 +1,4 @@
 //go:build integration
-// +build integration
 
 package main
 

cmd/osbuild-composer-dbjobqueue-tests/main_test.go

@@ -1,5 +1,4 @@
 //go:build integration
-// +build integration
 
 package main
 

cmd/osbuild-composer-manifest-tests/main_test.go

@@ -1,4 +1,4 @@
-// +build integration
+//go:build integration
 
 package main
 

cmd/osbuild-dnf-json-tests/main_test.go

@@ -1,7 +1,6 @@
 // This package contains tests related to dnf-json and rpmmd package.
 
 //go:build integration
-// +build integration
 
 package main
 

cmd/osbuild-image-tests/constants/constants.go

@@ -1,4 +1,4 @@
-// +build integration
+//go:build integration
 
 package constants
 

cmd/osbuild-image-tests/main_test.go

@@ -1,5 +1,4 @@
 //go:build integration
-// +build integration
 
 package main
 

cmd/osbuild-koji-tests/main_test.go

@@ -4,7 +4,6 @@
 // koji.sh test because it needs a working Koji instance to pass.
 
 //go:build integration
-// +build integration
 
 package main
 

cmd/osbuild-service-maintenance/db_test.go

@@ -1,5 +1,4 @@
 //go:build integration
-// +build integration
 
 package main