Correct convergence test

src/AMBER/background.py

@@ -617,7 +617,7 @@ class background():
         new_loss = 1000000
         k = 0
 
-        while (np.abs(old_loss - new_loss) > 1e-3) and (k < n_epochs):
+        while (old_loss - new_loss > 1e-3) and (k < n_epochs):
             # Compute A = Y - B by filling the nans with 0s
             A = np.where(np.isnan(Y_r - b_tmp) == True, 0.0, Y_r - b_tmp)