py-fuzzer: recommend using uvx rather than uv run to run the fuzzer

[AlexWaygood]

uvx --from=foo bar seems to accomplish the same thing as uv run --no-project --with=foo bar, but it's a fair bit less to type out on the command line

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.

Formatter (stable)

✅ ecosystem check detected no format changes.

Formatter (preview)

✅ ecosystem check detected no format changes.