Add monkey_test to input postsubmit

It needs to run for a bit in postsubmit before we can add it to
presubmit.

Bug: 328347986
Test: (cd frameworks/native/services/inputflinger && atest)
Change-Id: I69c622d2c766896e222bc0f2a8df441cf8496132
diff --git a/services/inputflinger/Android.bp b/services/inputflinger/Android.bp
index d244b1a..4184a08 100644
--- a/services/inputflinger/Android.bp
+++ b/services/inputflinger/Android.bp
@@ -270,5 +270,6 @@
         "FrameworksServicesTests",
         "CtsSecurityTestCases",
         "CtsSecurityBulletinHostTestCases",
+        "monkey_test",
     ],
 }