cmd/compile/internal/noder: remove TODO about position handling
cmd/compile/internal/noder: remove TODO about position handling

types2 uses nopos as the position for predeclared objects, so it's
expected that we'll see !pos.IsKnown() when translating types2
representations into IR.

Change-Id: I8708c2e9815e3dd27da8066c67c73f5586ac4617
Reviewed-on: https://go-review.googlesource.com/c/go/+/406896
Auto-Submit: Matthew Dempsky <e56ac2c500064424afac424d4b5e53bd0570a731@google.com>
Run-TryBot: Matthew Dempsky <e56ac2c500064424afac424d4b5e53bd0570a731@google.com>
Reviewed-by: Robert Griesemer <a6752097faebf1f02d80107d77a9be009089afe3@google.com>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

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