log: replace the outdated link (#29412)

log/format.go

@@ -340,7 +340,7 @@ func writeTimeTermFormat(buf *bytes.Buffer, t time.Time) {
 
 // writePosIntWidth writes non-negative integer i to the buffer, padded on the left
 // by zeroes to the given width. Use a width of 0 to omit padding.
-// Adapted from golang.org/x/exp/slog/internal/buffer/buffer.go
+// Adapted from pkg.go.dev/log/slog/internal/buffer
 func writePosIntWidth(b *bytes.Buffer, i, width int) {
 	// Cheap integer to fixed-width decimal ASCII.
 	// Copied from log/log.go.