This change fixes the remaining examples where the raw strings had
suboptimal indentation (one level too many) when viewed in godoc.

Follows CL 48910.
Fixes #21026.

Change-Id: Ifc0dae3fa899a9fff8b1ff958414e2fe6852321d
Reviewed-on: https://go-review.googlesource.com/50990
Run-TryBot: Dmitri Shuralyov <shurcool@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>