[SPARK-42419][FOLLOWUP][CONNECT][PYTHON] Remove unused exception

[itholic]

What changes were proposed in this pull request?

This is follow-up for #39991 to remove unused exception.

Why are the changes needed?

PySparkTypeError never raises because we checked the type already in the codes above if type(startPos) != type(length): and raise PySparkTypeError for unsupported type for length.

Does this PR introduce any user-facing change?

No. it's minor code cleanup

How was this patch tested?

The existing CI should pass.

[zhengruifeng]

to be more consistent with

spark/python/pyspark/sql/column.py

Lines 924 to 932 in a45affe

	if isinstance(startPos, int):
	jc = self._jc.substr(startPos, length)
	elif isinstance(startPos, Column):
	jc = self._jc.substr(startPos._jc, cast("Column", length)._jc)
	else:
	raise PySparkTypeError(
	error_class="NOT_COLUMN_OR_INT",
	message_parameters={"arg_name": "startPos", "arg_type": type(startPos).__name__},
	)

what about changing to?

        if isinstance(length, Column):
            length_expr = length._expr
            start_expr = startPos._expr
        elif isinstance(length, int):
            length_expr = LiteralExpression._from_value(length)
            start_expr = LiteralExpression._from_value(startPos)
        else:
            raise PySparkTypeError(
                error_class="NOT_COLUMN_OR_INT",
                message_parameters={"arg_name": "length", "arg_type": type(length).__name__},
            )          

[itholic]

what about changing to?

@zhengruifeng Nice! Just applied the comment

[zhengruifeng]

oh, the linter fails

[itholic]

Fixed!

[zhengruifeng]

merged to master