Prevent agnostic baker to be run without arguments

Prevents agnostic baker to be run without any baker arguments.

Manually testing the MR

./octez-agnostic-baker
Cannot run agnostic baker without any baker arguments. Please refer to the following help.
Usage:
  octez-agnostic-baker [OCTEZ-AGNOSTIC-BAKER-COMMANDS] -- [OCTEZ-BAKER-COMMANDS]

OCTEZ-AGNOSTIC-BAKER-COMMANDS:
  --help: display help
  --binaries-directory: path to the octez-baker binaries

OCTEZ-BAKER-COMMANDS:
 Run ./octez-baker-<PROTOCOL_HASH> --help

⚠ Don't forget to compile the binary:

$rm -rf octez-agnostic-baker && dune build src/bin_agnostic_baker/main_agnostic_baker.exe && mv _build/default/src/bin_agnostic_baker/main_agnostic_baker.exe octez-agnostic-baker

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR