Clear InputMethodManager.sInstance for SDK > P

This fixes a minor case of test pollution when a test interacts with a
TextView.

InputMethodManager.sInstance still gets populated in SDK > P, and it may
contain a reference to a ViewRootImpl (mCurRootView), which causes an Activity
to leak across tests.

PiperOrigin-RevId: 411153919

shadows/framework/src/main/java/org/robolectric/shadows/ShadowInputMethodManager.java

@@ -267,9 +267,10 @@ public static void reset() {
     _InputMethodManager_ _reflector = reflector(_InputMethodManager_.class);
     if (apiLevel <= JELLY_BEAN_MR1) {
       _reflector.setMInstance(null);
-    } else if (apiLevel <= P) {
-      _reflector.setInstance(null);
     } else {
+      _reflector.setInstance(null);
+    }
+    if (apiLevel > P) {
       _reflector.getInstanceMap().clear();
     }
   }