Update gpameter.user.js

[ujjwalpawar]

Added option of satisfactory grade introduced for the fall semester of 2020. It's similar to the Pass/No Pass (P/NP) grade present in many universities.

[SaiHarshaK]

Your PR breaks the functionality of the script.
The thing you have mentioned regarding Pass/No Pass (P/NP) grade is for audit courses that aren't required to be kept track of anyway. Moreover, you cannot generalize it by just checking S grade, because during the pandemic students were given a choice between S and letter grade. Your change would count these credits as "satisfactory" instead of the appropriate ones.