Fix: Update p3/rubric.md Q10 deduction

p3/rubric.md

@@ -70,7 +70,7 @@
   - `sales_sum_2021` variable is hard coded as 116806 (-5)
   - `year_sum` function is not used (-3)
   - Passed more arguments than necessary to `year_sum` function (-1)
-  - Default value for year=2019 is changed in `year_sum` function (-1)
+  - Default value for year=2021 is changed in `year_sum` function (-1)
 
 - Q11 deductions