grim/convey

Replace deprecated ioutil usage

5 months ago, Elliott Sales de Andrade
f2b1178f3266
Replace deprecated ioutil usage

It was deprecated in Go 1.16, but `go.mod` wants 1.17 already.

Testing Done:
Ran `go build .`

Reviewed at https://reviews.imfreedom.org/r/2868/
REVIEWBOARD_URL = "https://reviews.imfreedom.org/"
REPOSITORY = "grim/convey"
REPOSITORY_TYPE = "mercurial"
BRANCH = "default"
LAND_DEST_BRANCH = "default"
LAND_PUSH = False