Tests: Fix some perpetually-running timer tests

This wasn't a problem before, but the ticker is never stopped and so the event loop may keep running if it hasn't been explicitly stopped by the other test. The timer API definitely needs some work, but for now this band-aid should help a little bit.

Tests/BDD/timer-namespace.spec.lua

@@ -217,6 +217,7 @@ describe("C_Timer", function()
 			C_Timer.Pause(ticker)
 			waitFor(2 * 100 * MAXIMUM_EPSILON_MODIFIER)
 			assertEquals(callbackCalledCount, 0)
+			C_Timer.Stop(ticker)
 		end)
 	end)
 
@@ -246,6 +247,7 @@ describe("C_Timer", function()
 			C_Timer.Resume(ticker)
 			waitFor(2 * 100 * MAXIMUM_EPSILON_MODIFIER)
 			assertTrue(callbackCalledCount >= 1)
+			C_Timer.Stop(ticker)
 		end)
 	end)