Remove github.com/pkg/errors and replace with std library version

This is possible now that we no longer support go1.12 and brings
rclone into line with standard practices in the Go world.

This also removes errors.New and errors.Errorf from lib/errors and
prefers the stdlib errors package over lib/errors.

backend/fichier/object.go

@@ -2,11 +2,12 @@ package fichier
 
 import (
 	"context"
+	"errors"
+	"fmt"
 	"io"
 	"net/http"
 	"time"
 
-	"github.com/pkg/errors"
 	"github.com/rclone/rclone/fs"
 	"github.com/rclone/rclone/fs/hash"
 	"github.com/rclone/rclone/lib/rest"
@@ -122,7 +123,7 @@ func (o *Object) Update(ctx context.Context, in io.Reader, src fs.ObjectInfo, op
 	// Delete duplicate after successful upload
 	err = o.Remove(ctx)
 	if err != nil {
-		return errors.Wrap(err, "failed to remove old version")
+		return fmt.Errorf("failed to remove old version: %w", err)
 	}
 
 	// Replace guts of old object with new one