Docs: improve accuracy of pdb alias example (#102892)

Author: gaogaotiantian

Doc/library/pdb.rst

@@ -513,7 +513,7 @@ can be overridden by the local file.
    :file:`.pdbrc` file)::
 
       # Print instance variables (usage "pi classInst")
-      alias pi for k in %1.__dict__.keys(): print("%1.",k,"=",%1.__dict__[k])
+      alias pi for k in %1.__dict__.keys(): print(f"%1.{k} = {%1.__dict__[k]}")
       # Print instance variables in self
       alias ps pi self