ash: fix a format string in a unit test

The variable here is an `int64_t`. On arm, this should be `%lld`. PRId64
solves these things.

Bug: 1058218
Change-Id: Ic31d842d345e5fae667dbedc739bbd132707bc58
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2095941Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Commit-Queue: George Burgess <gbiv@chromium.org>
Cr-Commit-Position: refs/heads/master@{#748850}

ash/display/overscan_calibrator_unittest.cc

@@ -33,7 +33,7 @@ TEST_F(OverscanCalibratorTest, Rotation) {
   auto* display_manager = Shell::Get()->display_manager();
 
   int64_t display_id = display::Screen::GetScreen()->GetPrimaryDisplay().id();
-  std::string id_str = base::StringPrintf("%ld", display_id);
+  std::string id_str = base::StringPrintf("%" PRId64, display_id);
 
   auto* calibrator = StartCalibration(id_str);
   calibrator->UpdateInsets(gfx::Insets(100, 5, 10, 15));