DOC Correct the default value of values_format in plot_confusion_matrix (scikit-learn#15981)

Author: qinhanmin2014

sklearn/metrics/_plot/confusion_matrix.py

@@ -61,8 +61,7 @@ def plot(self, include_values=True, cmap='viridis',
 
         values_format : str, default=None
             Format specification for values in confusion matrix. If `None`,
-            the format specification is '.2f' for a normalized matrix, and
-            'd' for a unnormalized matrix.
+            the format specification is '.2g'.
 
         ax : matplotlib axes, default=None
             Axes object to plot on. If `None`, a new figure and axes is
@@ -165,8 +164,7 @@ def plot_confusion_matrix(estimator, X, y_true, labels=None,
 
     values_format : str, default=None
         Format specification for values in confusion matrix. If `None`,
-        the format specification is '.2f' for a normalized matrix, and
-        'd' for a unnormalized matrix.
+        the format specification is '.2g'.
 
     cmap : str or matplotlib Colormap, default='viridis'
         Colormap recognized by matplotlib.