Fix business days calculations

[jedrekdomanski]

Reference

#196

Description

When calculating the next business day using BusinessDays#calculate_after, the method incorrectly advances one extra day if the starting point is a weekend or holiday.

Example (before fix):

# Saturday, Sept 6, 2025
1.business_day.after(Date.parse("2025-09-06"))
# => Tuesday, Sept 9, 2025 (❌ incorrect)

Expected behavior:

The method should stop on the first business day, which is Monday, Sept 8, 2025.

# Saturday, Sept 6, 2025
1.business_day.after(Date.parse("2025-09-06"))
# => Monday, Sept 8, 2025 (✅  correct)

[rodrigofhm]

Thank you for the fix @jedrekdomanski !

We forked your repo!