update KBCG20 mean_residual_Seattle_basin coeff at 2.0 and 3.0 sec
update KBCG20 mean_residual_Seattle_basin coeff at 2.0 and 3.0 sec. new values from KBCG20 GitHub repo (https://github.com/nikuehn/KBCG20/blob/5d30338436b897822b411553c6ae0bf31fac5ce5/COEFFS_SEP21/coefficients_KBCG20.csv), rounded to 16 decimal places. Accepted modified test results.
Resolves #162 (closed)
Edited by Altekruse, Jason Morgan