devtools/docker: sort environment variables
devtools/docker: sort environment variables

The environment sections are sorted alphabetically.

Change-Id: I9a9342d2c1ef23edfc37b01c617561dc6ed57b06
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/329914
Trust: Julie Qiu <8d32267b6b4884cf35adeaccde2b6857ae11aace@golang.org>
Run-TryBot: Julie Qiu <8d32267b6b4884cf35adeaccde2b6857ae11aace@golang.org>
Reviewed-by: Jonathan Amsterdam <e3d3698b2ccd5955e4adf250d0785062d0f9018b@google.com>

golang/pkgsite,golang/pkgsite,golang/pkgsite,golang/pkgsite