Removed deprecated ruff rule E999 from ruff.toml

[EGJ-Moorington]

Removed the check for rule E999 (sintax-error), which has been deprecated, from ruff.toml. According to the documentation:

Syntax errors will always be shown regardless of whether this rule is selected or not.

Using this rule produced an error when running the ruff pre-commit hook:

ruff (legacy alias)......................................................Failed

• hook id: ruff
• exit code: 2

ruff failed
Cause: Rule E999 was removed and cannot be selected.

Resolves #249

[FoamyGuy]

Thank you.

Note to self: It would probably good at some point to use adabot to patch this change to the rest of the library repos as well.