docs: drop the grids.yaml bullet from the config README

The README listed grids.yaml among the files in this directory, but the
directory has not contained one since the radial_minimum consumer was removed
(025ac7ac, 2025-10-15). The remaining downstream copies are deleted in the same
sweep.

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

autoarray/config/README.md

@@ -8,6 +8,5 @@ The `config` folder contains configuration files which customize default **PyAut
 # Files
 
 - `general.yaml`: Customizes general **PyAutoLens** settings.
-- `grids.yaml`: Customize default behaviour of grids when used for calculations.
 - `logging.yaml`: Customizes the logging behaviour.
 - `notation.yaml`: Configs defining labels and formatting of model parameters when used for visualization.