doc/go1.17: remove lingering TODO
doc/go1.17: remove lingering TODO

As far as I can tell the Core Library section is complete. Remove its
TODO.

Change-Id: Ia84c6656fac045e25fae1a7ce8b488a3a26fd250
Reviewed-on: https://go-review.googlesource.com/c/go/+/326469
Trust: Heschi Kreinick <e89ab2b172855aa0ad01c40c4d8a3535a61ac68a@google.com>
Run-TryBot: Heschi Kreinick <e89ab2b172855aa0ad01c40c4d8a3535a61ac68a@google.com>
TryBot-Result: Go Bot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Dmitri Shuralyov <d181b7fea0ec87c86ba5a890ab716db52498e3ba@golang.org>
Reviewed-by: Damien Neil <7e091e9a80da888fcd7836fd3c6b7b85f4677c12@google.com>

CAFxX/go,CAFxX/go,nawawi/go,CAFxX/go,CAFxX/go,cloudflare/go,nawawi/go,golang/go,golang/go,cloudflare/go,cloudflare/go,cloudflare/go,nawawi/go,cloudflare/go,nawawi/go,CAFxX/go,nawawi/go,golang/go,CAFxX/go,golang/go,cloudflare/go,golang/go,nawawi/go,golang/go,CAFxX/go,golang/go,cloudflare/go,CAFxX/go,nawawi/go,golang/go,nawawi/go,cloudflare/go