fix: use PEP 440 direct URL syntax instead of deprecated #egg= fragment

[aldbr]

Summary

• Replace deprecated #egg= fragment syntax with PEP 440 direct URL syntax (name[extra] @ URL) in pilotCommands.py
• Fixes pip install failures when using --modules with pip >= 25.0, which rejects #egg= fragments with error: invalid-egg-fragment

Motivation

Since pip 25.0 (January 2025), the #egg= URL fragment is no longer accepted and raises an invalid-egg-fragment error:

× The 'DIRAC[pilot]' egg fragment is invalid
╰─> from 'git+https://github.com/ryuwd/DIRAC.git@feat/cwl-job-submission#egg=DIRAC[pilot]'

hint: Try using the Direct URL requirement syntax: 'name[extra] @ URL'

This breaks any pilot installation using the modules option (e.g. url:::project:::branch syntax) to install a non-released DIRAC version from a git repository.

Changes

# Before
pip install git+https://github.com/fstagni/DIRAC.git@v7r2-fixes33#egg=DIRAC[pilot]

# After
pip install DIRAC[pilot] @ git+https://github.com/fstagni/DIRAC.git@v7r2-fixes33

[aldbr]

Closing because not coming from my fork.
Here is the right one: #281