cli/command: remove usages of RegistryAuthenticationPrivilegedFunc

This patch deprecates the unused `RegistryAuthenticationPrivilegedFunc`.
The function would prompt the user when the registry returns a 403 after trying
the initial auth value set in `RegistryAuth`.

Signed-off-by: Alano Terblanche <[email protected]>

Author: Benehiko

cli/command/registry.go

@@ -36,6 +36,8 @@ const authConfigKey = "https://index.docker.io/v1/"
 
 // RegistryAuthenticationPrivilegedFunc returns a RequestPrivilegeFunc from the specified registry index info
 // for the given command to prompt the user for username and password.
+//
+// Deprecated: this function is no longer used and will be removed in the next release.
 func RegistryAuthenticationPrivilegedFunc(cli Cli, index *registrytypes.IndexInfo, cmdName string) registrytypes.RequestAuthConfig {
 	configKey := getAuthConfigKey(index.Name)
 	isDefaultRegistry := configKey == authConfigKey || index.Official