internal/task: remove TODO comment in ConvertPKGToTGZ
internal/task: remove TODO comment in ConvertPKGToTGZ

The default normalization that adjustTar applies is sufficient for
the needs of ConvertPKGToTGZ. There are no additional adjustments
needed since they've already been applied in earlier stages.

This was expected, and a test run hasn't uncovered anything more
to change here, so remove the resolved TODO comment.

For golang/go#53632.

Change-Id: I024bf5fd739ab07200b7f2339f68cfe340a594c3
Reviewed-on: https://go-review.googlesource.com/c/build/+/447959
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Run-TryBot: Dmitri Shuralyov <d181b7fea0ec87c86ba5a890ab716db52498e3ba@golang.org>
Reviewed-by: Dmitri Shuralyov <d181b7fea0ec87c86ba5a890ab716db52498e3ba@google.com>
Reviewed-by: Carlos Amedee <ab5e2bca84933118bbc9d48ffaccce3bac4eeb64@golang.org>

golang/build,golang/build,golang/build,golang/build