Allow negative shift year for fiscal periods

[boludo00]

Some fiscal years are tracked differently, needing support of a negative shift year.
For example, in one scenario a date_day of 2022-01-01 is actually in the fiscal year 2023. The generated fiscal_year_number would need to be 2023 in this case. This can be achieved by suppling a negative shift value however, doing so causes the rendered SQL to be interpreted as a comment:

{{ dbt_date.get_fiscal_periods(ref('dates'), year_end_month=1, week_start_day=2, shift_year=-1) }}

d.year_number -{{ shift_year }} as fiscal_year_number,

Gets rendered as:

d.year_number --1 as fiscal_year_number, this is a comment 👀 

Not sure how everyone else's use case differs, but I thought I would bring it up in case there are more similar scenarios out there.

[clausherther]

Good call, thanks for raising that issue!