internal/abi: update type name in comment

internal/abi: update type name in comment

method -> Method

For #59670

Change-Id: I78e0410f3d5094aa12b2f3ccd6735fec0d696190
Reviewed-on: https://go-review.googlesource.com/c/go/+/494795
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@google.com>