devapp/owners: add myself to encoding/json
devapp/owners: add myself to encoding/json

Done more stuff there recently and it needs attention, so it seems like
a right fit.

Change-Id: I6344ccc5da83c0cfecd7a7f2ecc1399497e0de03
Reviewed-on: https://go-review.googlesource.com/131285
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/build,golang/build,golang/build,golang/build