chacha20poly1305: fix typos
chacha20poly1305: fix typos

Change-Id: I55a2ad4495f4e1164af6a8504b035cf658f8b822
Reviewed-on: https://go-review.googlesource.com/34536
Run-TryBot: Mikio Hara <e2f4d2eec1d9a1f781345cdd7260d7d52e6468ae@gmail.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/crypto,golang/crypto,golang/crypto,ScriptRock/crypto,ScriptRock/crypto