test(ngMock): fix Firefox craches on Travis

This test keeps causing Firefox 47 (currently used on Travis) to crash and fail
the build. The test passes locally (on Firefox 53). Lowering the loop count from
1000 to 100 seems to fix the issue.
(Note: The crach only affects the mocked implementation of `$interval` and does
not happen locally.)

Closes #16040

test/ngMock/angular-mocksSpec.js

@@ -358,12 +358,12 @@ describe('ngMock', function() {
       $interval(function() { counterA++; });
       $interval(function() { counterB++; }, 0);
 
-      $interval.flush(1000);
-      expect(counterA).toBe(1000);
-      expect(counterB).toBe(1000);
-      $interval.flush(1000);
-      expect(counterA).toBe(2000);
-      expect(counterB).toBe(2000);
+      $interval.flush(100);
+      expect(counterA).toBe(100);
+      expect(counterB).toBe(100);
+      $interval.flush(100);
+      expect(counterA).toBe(200);
+      expect(counterB).toBe(200);
     }));