chore: delete defunct config/grids.yaml

The radial_minimum mapping in config/grids.yaml has not been read by any code
since PyAutoGalaxy 025ac7ac "remove relocate_to_radial_minimum" (2025-10-15),
which followed 82622f74 "remove grid relocate radial" (2025-04-03). The library
default configs no longer ship a grids.yaml at all; only these downstream copies
survived.

Verified: zero .py hits for radial_minimum across PyAutoArray, PyAutoGalaxy,
PyAutoLens, PyAutoCTI and PyAutoNerves, and zero hits in the installed venv.
Profiles still evaluate finitely at exactly (0.0, 0.0) - the case the config
used to guard is handled in code.

Issue: PyAutoLabs/autolens_workspace#317

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WGnmAUuQwTSCnp8U5dD3ee

Author: 2 people