podman: drop checking valid rootless UID

do not check whether the specified ID is valid in the user namespace.

crun handles this case[1], so the check in Podman prevents to get to
the OCI runtime at all.

$ podman run --user 10:0 --uidmap 0:0:1 --rm -ti fedora:33 sh -c 'id; cat /proc/self/uid_map'
uid=10(10) gid=0(root) groups=0(root),65534(nobody)
        10          0          1

[1] https://github.com/containers/crun/pull/556

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

pkg/util/utils_linux.go

@@ -6,7 +6,6 @@ import (
 	"path/filepath"
 	"syscall"
 
-	"github.com/containers/podman/v2/pkg/rootless"
 	"github.com/containers/psgo"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
@@ -53,19 +52,3 @@ func FindDeviceNodes() (map[string]string, error) {
 
 	return nodes, nil
 }
-
-// CheckRootlessUIDRange checks the uid within the rootless container is in the range from /etc/subuid
-func CheckRootlessUIDRange(uid int) error {
-	uids, _, err := rootless.GetConfiguredMappings()
-	if err != nil {
-		return err
-	}
-	total := 0
-	for _, u := range uids {
-		total += u.Size
-	}
-	if uid > total {
-		return errors.Errorf("requested user's UID %d is too large for the rootless user namespace", uid)
-	}
-	return nil
-}