Replace errors.Cause() with errors.Is()

Dependencies may be switching to use the new `%w` formatting
option to wrap errors; switching to use `errors.Is()` makes
sure that we are still able to unwrap the error and detect the
underlying cause.

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

remotes/docker/pusher.go

@@ -86,7 +86,7 @@ func (p dockerPusher) Push(ctx context.Context, desc ocispec.Descriptor) (conten
 
 	resp, err := req.doWithRetries(ctx, nil)
 	if err != nil {
-		if errors.Cause(err) != ErrInvalidAuthorization {
+		if !errors.Is(err, ErrInvalidAuthorization) {
 			return nil, err
 		}
 		log.G(ctx).WithError(err).Debugf("Unable to check existence, continuing with push")