cmd/compile/internal/types2: reduce output when describing type parameters
cmd/compile/internal/types2: reduce output when describing type parameters

There's no need to say "type parameter" for a type parameter. The
name is sufficient (they are always named), and the prose is followed
by "constrained by".

Change-Id: I98df8caa1432b8b7a874e58da6e3ed6be102b4a0
Reviewed-on: https://go-review.googlesource.com/c/go/+/357410
Trust: Robert Griesemer <a6752097faebf1f02d80107d77a9be009089afe3@golang.org>
Run-TryBot: Robert Griesemer <a6752097faebf1f02d80107d77a9be009089afe3@golang.org>
TryBot-Result: Go Bot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Robert Findley <9179eee875d1ee628c37fb47d7e749e855ffd21f@google.com>

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