doc: remove egg fragment from dev/developer_guide/running-tests-locally
DEPRECATION: git+https://github.com/ceph/teuthology#egg=teuthology
[test] contains an egg fragment with a non-PEP 508 name pip 25.0 will enforce
this behaviour change. A possible replacement is to use the req @ url syntax,
and remove the egg fragment. Discussion can be found at
https://github.com/pypa/pip/issues/11617