Specifying --env without specifying --app for 'task run' produces confusing error message

[andyspix]

This is a minor nit to pick, but when specifying to run a task and the --env field is passed without a corresponding --app flag, ie:

copilot task run --env staging --entrypoint entrypoints/test_task.sh

the tool returns:
✘ could not find an application attached to this workspace, please run app init first

when an application exists, and of course app init doesn't fix the issue, which is actually an incompletely specified command line:

copilot task run --app foobar --env staging --entrypoint entrypoints/test_task.sh