Port null/NaN validation text from iOS (#613)

* Update Firestore run configuration for Android Studio 3.4.1

* Port null/NaN validation text from iOS

From firebase/firebase-ios-sdk#2670

Author: wilhuff

.idea/runConfigurations/Firestore_Integration_Tests__Firestore_Emulator_.xml

@@ -400,10 +400,10 @@ public void queriesWithNullOrNaNFiltersOtherThanEqualityFail() {
     CollectionReference collection = testCollection();
     expectError(
         () -> collection.whereGreaterThan("a", null),
-        "Invalid Query. You can only perform equality comparisons on null (via whereEqualTo()).");
+        "Invalid Query. Null supports only equality comparisons (via whereEqualTo()).");
     expectError(
         () -> collection.whereArrayContains("a", null),
-        "Invalid Query. You can only perform equality comparisons on null (via whereEqualTo()).");
+        "Invalid Query. Null supports only equality comparisons (via whereEqualTo()).");
     expectError(
         () -> collection.whereArrayContainsAny("a", null),
         "Invalid Query. A non-empty array is required for 'array_contains_any' filters.");
@@ -413,10 +413,10 @@ public void queriesWithNullOrNaNFiltersOtherThanEqualityFail() {
 
     expectError(
         () -> collection.whereGreaterThan("a", Double.NaN),
-        "Invalid Query. You can only perform equality comparisons on NaN (via whereEqualTo()).");
+        "Invalid Query. NaN supports only equality comparisons (via whereEqualTo()).");
     expectError(
         () -> collection.whereArrayContains("a", Double.NaN),
-        "Invalid Query. You can only perform equality comparisons on NaN (via whereEqualTo()).");
+        "Invalid Query. NaN supports only equality comparisons (via whereEqualTo()).");
   }
 
   @Test

firebase-firestore/src/androidTest/java/com/google/firebase/firestore/ValidationTest.java

@@ -82,15 +82,13 @@ public static FieldFilter create(FieldPath path, Operator operator, FieldValue v
     } else if (value.equals(NullValue.nullValue())) {
       if (operator != Filter.Operator.EQUAL) {
         throw new IllegalArgumentException(
-            "Invalid Query. You can only perform equality comparisons on null (via "
-                + "whereEqualTo()).");
+            "Invalid Query. Null supports only equality comparisons (via whereEqualTo()).");
       }
       return new FieldFilter(path, operator, value);
     } else if (value.equals(DoubleValue.NaN)) {
       if (operator != Filter.Operator.EQUAL) {
         throw new IllegalArgumentException(
-            "Invalid Query. You can only perform equality comparisons on NaN (via "
-                + "whereEqualTo()).");
+            "Invalid Query. NaN supports only equality comparisons (via whereEqualTo()).");
       }
       return new FieldFilter(path, operator, value);
     } else if (operator == Operator.ARRAY_CONTAINS) {