Bug 1705181 - Adjust rAF rate for asyncScriptsSuspendedWhileInactive. r=owlish

The 500ms value was completely arbitrary (we're trying to test that the rAF
rate is reduced, not that it's exactly 500ms), looks like in some cases we get
updates _just_ below the 500ms mark, so to avoid false failures we can reduce
the value to 450ms.

Differential Revision: https://phabricator.services.mozilla.com/D115744

mobile/android/geckoview/src/androidTest/java/org/mozilla/geckoview/test/SessionLifecycleTest.kt

@@ -174,7 +174,7 @@ class SessionLifecycleTest : BaseSessionTest() {
 
         var rafRate = computeRequestAnimationFrameRate(mainSession)
         assertThat("requestAnimationFrame should be called about once a second",
-            rafRate, greaterThan(500.0))
+            rafRate, greaterThan(450.0))
         assertThat("requestAnimationFrame should be called about once a second",
                 rafRate, lessThan(10000.0))