Backport PR #38841: Update conf.py to execute imports during pdf building (#38970)

Co-authored-by: WANG Aiyong <[email protected]>

Author: meeseeksmachine

doc/source/conf.py

@@ -427,7 +427,7 @@
 
 
 ipython_warning_is_error = False
-ipython_exec_lines = [
+ipython_execlines = [
     "import numpy as np",
     "import pandas as pd",
     # This ensures correct rendering on system with console encoding != utf8