Update libkv dependency

vendor/golang.org/x/text/width/width.go

@@ -153,17 +153,22 @@ func (p Properties) Wide() rune {
 
 // Transformer implements the transform.Transformer interface.
 type Transformer struct {
-	t transform.Transformer
+	t transform.SpanningTransformer
 }
 
 // Reset implements the transform.Transformer interface.
 func (t Transformer) Reset() { t.t.Reset() }
 
-// Transform implements the Transformer interface.
+// Transform implements the transform.Transformer interface.
 func (t Transformer) Transform(dst, src []byte, atEOF bool) (nDst, nSrc int, err error) {
 	return t.t.Transform(dst, src, atEOF)
 }
 
+// Span implements the transform.SpanningTransformer interface.
+func (t Transformer) Span(src []byte, atEOF bool) (n int, err error) {
+	return t.t.Span(src, atEOF)
+}
+
 // Bytes returns a new byte slice with the result of applying t to b.
 func (t Transformer) Bytes(b []byte) []byte {
 	b, _, _ = transform.Bytes(t, b)