fix parser diagnostic regression when the error points to an empty span immediately after a line terminator

[BurntSushi]

While #15359 fixed a ton of bugs with our diagnostic rendering, it did introduce one regression related to parser diagnostics. Specifically, prior to #15359, we would get the following diagnostic in one case of a syntax error:

   |
12 | exept:  # spellchecker:disable-line
13 |     pass
14 | b = 1
   |  Syntax Error: Expected a statement
   |

(This is from crates/ruff_python_parser/tests/snapshots/invalid_syntax@try_stmt_misspelled_except.py.snap.)

Now, the ^ is missing from the above. After #15359, the caret is added, but the diagnostic is now pointing at the end of the preceding line:

   |
12 | exept:  # spellchecker:disable-line
13 |     pass
   |         ^ Syntax Error: Expected a statement
14 | b = 1
   |

We might be able to fix this by tweaking the ranges emitted by the parser when creating a diagnostic:

ruff/crates/ruff_python_parser/src/parser/mod.rs

Lines 489 to 492 in 96da136

	self.add_error(
	recovery_context_kind.create_error(self),
	self.current_token_range(),
	);

But I think it would probably be better to fix the renderer itself so that it points to the beginning of the following line automatically.

See #15509 which is related to this issue. These issues are technically separate since this one could be fixed independently of #15509. But if #15509 is fixed, then I think this one will automatically resolve itself as well.