Dockerfile.test.yml: Set CI=1

Set CI=1 to disable this warning.

==> brew doctor
Please note that these warnings are just used to help the Homebrew maintainers
with debugging if you file an issue. If everything you use Homebrew for is
working fine: please don't worry or file an issue; just ignore this. Thanks!
Warning: git origin remote is Linuxbrew/brew.
Linuxbrew/brew has been merged into Homebrew/brew!
Linuxbrew/brew will no longer be updated.
The current git origin is:
https://github.com/Linuxbrew/brew
Please set the origin remote to point at the Homebrew/brew by running:
git -C "/home/linuxbrew/.linuxbrew/Homebrew" remote set-url origin https://github.com/Homebrew/brew
==> FAILED

Author: sjackman

Dockerfile.test.yml

@@ -1,3 +1,3 @@
 sut:
   build: .
-  command: brew test-bot
+  command: env CI=1 brew test-bot