gh-153395: Fix test_complexchar on narrow curses builds (GH-154005)

On a narrow build, complexchar() of a multibyte character raises
OverflowError, not ValueError.

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: serhiy-storchaka

Lib/test/test_curses.py

@@ -2799,9 +2799,11 @@ def test_complexchar(self):
         # its single character.  A narrow build just forms fewer cells.
         cc = curses.complexchar
         def storable(s):
+            # ValueError if s has combining marks on a narrow build.
+            # OverflowError if s is a multibyte character on a narrow build.
             try:
                 cc(s)
-            except ValueError:
+            except (ValueError, OverflowError):
                 return False
             return True