Remove note on introduction of sig_figs.

Co-authored-by: Brian Ward <brianmward99@gmail.com>

Author: tillahoffmann

cmdstanpy/model.py

@@ -1667,7 +1667,6 @@ def log_prob(
         :param sig_figs: Numerical precision used for output CSV and text files.
             Must be an integer between 1 and 18.  If unspecified, the default
             precision for the system file I/O is used; the usual value is 6.
-            Introduced in CmdStan-2.25.
 
         :return: A pandas.DataFrame containing columns "lp__" and additional
             columns for the gradient values. These gradients will be for the