ci: Move documentation to correct config file

ci/test/00_setup_env_mac.sh

@@ -7,6 +7,7 @@
 export LC_ALL=C.UTF-8
 
 export CONTAINER_NAME=ci_macos_cross
+export DOCKER_NAME_TAG=ubuntu:18.04  # Check that bionic can cross-compile to macos (bionic is used in the gitian build as well)
 export HOST=x86_64-apple-darwin16
 export PACKAGES="cmake imagemagick libcap-dev librsvg2-bin libz-dev libbz2-dev libtiff-tools python3-dev python3-setuptools"
 export XCODE_VERSION=11.3.1

ci/test/00_setup_env_mac_host.sh

@@ -7,7 +7,6 @@
 export LC_ALL=C.UTF-8
 
 export HOST=x86_64-apple-darwin16
-export DOCKER_NAME_TAG=ubuntu:18.04  # Check that bionic can cross-compile to macos (bionic is used in the gitian build as well)
 export PIP_PACKAGES="zmq"
 export GOAL="install"
 export BITCOIN_CONFIG="--with-gui --enable-reduce-exports --enable-werror --with-boost-process"