#15109: revert '%'->'format' changes in 4b105d328fe7 to fix regression.

With '%', non-ascii worked because the '%' automatically got promoted to
unicode.  With format that doesn't happen, which led to encoding errors.  This
fix goes back to using %, and adds a test to make sure non-ascii string values
work in iterdump.
diff --git a/Misc/NEWS b/Misc/NEWS
index 6bb2549..469ca8b 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -186,6 +186,10 @@
 Library
 -------
 
+- Issue #15109: Fix regression in sqlite3's iterdump method where it would
+  die with an encoding error if the database contained string values
+  containing non-ASCII.  (Regression was introduced by fix for 9750).
+
 - Issue #15545: Fix regression in sqlite3's iterdump method where it was
   failing if the connection used a row factory (such as sqlite3.Row) that
   produced unsortable objects. (Regression was introduced by fix for 9750).