Remove conditional ticker previous value updating

I'm not sure why it was only conditionally updating the values before
because running the comparisons as `if` checks is slower than just
always replacing fields with the new values each time.

The only edge cases this would impact is if instruments received many
last trades all of the same price and size (3x3, 5x5, 5x5, 5x5) after
each other, the previous way would always show previousPrice/Size as 3x3
until a new value was received, but that's also a lie because the
_previous_ reported trade was the _same_ as the current trade.

Now this is both more accurate to the truth (especially since we have
`lastTimestamp` being reported from the API now) and faster since it
isn't doing multiple comparisons to just set the same fields each time.

Author: mattsta

ib_async/wrapper.py

@@ -902,33 +902,29 @@ def priceSizeTick(self, reqId: int, tickType: int, price: float, size: float):
                 price = self.defaultEmptyPrice
                 size = self.defaultEmptySize
 
-            # only update if there is a new price/size combination
-            if (price, size) != (ticker.bid, ticker.bidSize):
-                ticker.prevBid = ticker.bid
-                ticker.prevBidSize = ticker.bidSize
-                ticker.bid = price
-                ticker.bidSize = size
+            ticker.prevBid = ticker.bid
+            ticker.prevBidSize = ticker.bidSize
+            ticker.bid = price
+            ticker.bidSize = size
         elif tickType in {2, 67}:
             if size == 0:
                 price = self.defaultEmptyPrice
                 size = self.defaultEmptySize
 
-            if (price, size) != (ticker.ask, ticker.askSize):
-                ticker.prevAsk = ticker.ask
-                ticker.prevAskSize = ticker.askSize
-                ticker.ask = price
-                ticker.askSize = size
+            ticker.prevAsk = ticker.ask
+            ticker.prevAskSize = ticker.askSize
+            ticker.ask = price
+            ticker.askSize = size
         elif tickType in {4, 68}:
             # for 'last' values, price can be valid with size=0 for updates like 'last SPX price' since SPX doesn't trade
             if price == -1 and size == 0:
                 price = self.defaultEmptyPrice
                 size = self.defaultEmptySize
 
-            if (price, size) != (ticker.last, ticker.lastSize):
-                ticker.prevLast = ticker.last
-                ticker.prevLastSize = ticker.lastSize
-                ticker.last = price
-                ticker.lastSize = size
+            ticker.prevLast = ticker.last
+            ticker.prevLastSize = ticker.lastSize
+            ticker.last = price
+            ticker.lastSize = size
         else:
             assert (
                 tickType in PRICE_TICK_MAP