doc/go1.20: add TODOs found by x/build/cmd/relnote
doc/go1.20: add TODOs found by x/build/cmd/relnote

Change-Id: Id1e7cf8f088fa39d177a001e97c93cd660d0b3c6
Reviewed-on: https://go-review.googlesource.com/c/go/+/450256
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Auto-Submit: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>
Run-TryBot: Russ Cox <5ad239cb8a44f659eaaee0aa1ea5b94947abe557@golang.org>
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@google.com>

golang/go,golang/go,golang/go,golang/go,golang/go,golang/go,golang/go,golang/go