[libc][NFC] Fix onre more -Wconversion warning in strtoul test code.

The last change missed one spot.

Differential Revision: https://reviews.llvm.org/D108845

GitOrigin-RevId: 225eb8a22d416c1c7405770165c3291ab0ee3dba
diff --git a/test/src/stdlib/strtoul_test.cpp b/test/src/stdlib/strtoul_test.cpp
index 16ca6b0..7b08a39 100644
--- a/test/src/stdlib/strtoul_test.cpp
+++ b/test/src/stdlib/strtoul_test.cpp
@@ -227,7 +227,7 @@
             } else {
               errno = 0;
               ASSERT_EQ(__llvm_libc::strtoul(small_string, nullptr, base),
-                        first_digit);
+                        static_cast<unsigned long int>(first_digit));
               ASSERT_EQ(errno, 0);
             }
           } else {