Fix parsing of unversioned cask packages.

[kdeldycke]

Unversioned cask packages are not properly parsed.

If cask outputs:

$ brew cask list --versions
bitcoin-core 
$

Then mpm fails to parse the output because of trailing spaces clean up:

Traceback (most recent call last):
  File "./meta_package_manager.7h.py", line 619, in <module>
    print_menu()
  File "./meta_package_manager.7h.py", line 568, in print_menu
    map(methodcaller('sync'), managers)
  File "./meta_package_manager.7h.py", line 243, in sync
    name, versions = installed_pkg.split(' ', 1)
ValueError: need more than 1 value to unpack

This PR fix the issue:

[github-actions]

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