Change default observed for pivot table

Author: jseabold

pandas/core/frame.py

@@ -6857,7 +6857,7 @@ def pivot_table(
         margins=False,
         dropna=True,
         margins_name="All",
-        observed=False,
+        observed=None,
     ) -> DataFrame:
         from pandas.core.reshape.pivot import pivot_table
 

pandas/core/reshape/pivot.py

@@ -45,7 +45,7 @@ def pivot_table(
     margins=False,
     dropna=True,
     margins_name="All",
-    observed=False,
+    observed=None,
 ) -> "DataFrame":
     index = _convert_by(index)
     columns = _convert_by(columns)