Update dev/setup_env_osx.sh

Co-authored-by: Carl Johnson <[email protected]>

Author: Peter Mounce

dev/setup_env_osx.sh

@@ -34,5 +34,5 @@ if ! p4d -V | grep '2018.2'; then
 fi
 
 if ! [[ -x "$(command -v bk)" ]]; then
-  echo "WARNING: $(bk) cli is not installed. https://github.com/buildkite/cli"
+  echo "WARNING: 'bk' cli is not installed. https://github.com/buildkite/cli"
 fi