Make UntrustedSpy_AbortsDispatcher threadsafe

A similar fix worked for the other dispatcher death test. The test
UntrustedSpy_AbortsDispatcher is a lot less flakier, with a fail rate of
about 1 in 1502.

Still, we want to achieve a near-zero flake rate, so apply the same fix
here.

Bug: 291797922
Test: TEST=inputflinger_tests; m $TEST && $ANDROID_HOST_OUT/nativetest64/$TEST/$TEST
Change-Id: Ic4a759862f110a24f7b239b9e20fa0222fd6668d
diff --git a/services/inputflinger/tests/InputDispatcher_test.cpp b/services/inputflinger/tests/InputDispatcher_test.cpp
index 609e4dd..7051680 100644
--- a/services/inputflinger/tests/InputDispatcher_test.cpp
+++ b/services/inputflinger/tests/InputDispatcher_test.cpp
@@ -9015,6 +9015,7 @@
  * Adding a spy window that is not a trusted overlay causes Dispatcher to abort.
  */
 TEST_F(InputDispatcherSpyWindowDeathTest, UntrustedSpy_AbortsDispatcher) {
+    testing::GTEST_FLAG(death_test_style) = "threadsafe";
     ScopedSilentDeath _silentDeath;
 
     auto spy = createSpy();