⬆️ aiida-shell: bump fork pin to simpler PR

aiidateam/aiida-shell#116 was updated to drop the `ShellCode.Model`
override entirely instead of feature-detecting both aiida-core model
APIs. The pin in `pyproject.toml` already points at
`GeigerJ2/aiida-shell@fix/installedcode-model-rename` (branch name
unchanged), so this commit only re-locks `uv.lock` to the new HEAD on
that branch.

The simpler approach works because both old and new aiida-core filter
`None` field values in their model -> ORM conversion, so the `__init__`
default of `'core.shell'` is the actual source of the behavior; the
nested `Model` override only ever shadowed that default for the `verdi
code create core.code.shell --help` cosmetic display.

Author: GeigerJ2