fix: sync/rate fixes rate:wait() on infinite rps

	* rate:wait() crashed for rates with infinite rps _reserve
	must return numeric `timeToAct` if reservation is allowed

sync/rate.lua

@@ -123,12 +123,12 @@ end
 ---@return boolean|sync.rate.reservation reservation, any? error_or_time_to_act
 function rate:_reserve(time, n, wait)
     if self.rps == math.huge then
-        return true
+        return true, time
     end
     if self.rps == 0 then
         if self.burst >= n then
             self.burst = self.burst - n
-            return true
+            return true, time
         end
         return false, "not enough burst"
     end

test/06-limit.test.lua

@@ -112,7 +112,7 @@ test:deadline(function()
 
 		test:ok(almost_gt(reserv.timeToAct, fiber.time()+1/rate.rps, 0.01), "timeToAct ≥ now+1/rps")
 		test:ok(almost_gt(fiber.time()+2/rate.rps, reserv.timeToAct, 0.01), "timeToAct ≤ now+2/rps")
-		reserv:cancel() -- cancell reservation
+		reserv:cancel() -- cancel reservation
 
 		reserv = rate:reserve()
 		assert(reserv)
@@ -142,6 +142,9 @@ test:deadline(function()
 		for _ = 1, 5 do
 			test:ok(rate:allow(), "infinite rate almost allows")
 		end
+		for _ = 1, 5 do
+			test:ok(rate:wait(), "infinite rate never waits")
+		end
 	end)
 
 end, 3, "rps=inf")