Tests: Fix some perpetually-running timer tests

Not sure why this wasn't a problem before, but the ticker is never stopped and so the event loop may keep running if it has been invoked once. The timer API (and tests) definitely need a rework, but for now this band-aid should help at least 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)