internal: remove // import comments

These comments were added to enforce using the correct import path for
our packages ("github.com/docker/docker", not "github.com/moby/moby").
However, when working in go module mode (not GOPATH / vendor), they have
no effect, so their impact is limited.

Remove these imports in preparation of migrating our code to become an
actual go module.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

internal/mounttree/switchroot_linux.go

@@ -1,4 +1,4 @@
-package mounttree // import "github.com/docker/docker/internal/mounttree"
+package mounttree
 
 import (
 	"fmt"

internal/unshare/unshare_linux.go

@@ -1,6 +1,6 @@
 //go:build go1.10
 
-package unshare // import "github.com/docker/docker/internal/unshare"
+package unshare
 
 import (
 	"fmt"