fix(SimpleWeb.jslib): Remove Runtime from global scope

In unity 2021 LTS or later, Runtime is not defined by Unity, so a fix was to define it ourselves, but the code was defining it in global scope, so if a 2nd unity webgl instance is created then it would use the Runtime variable from the first one, which caused various errors.

Dropping support for older unity versions means we can go back to using dynCall directly instead of calling via Runtime.dynCall

Author: MrGadget1024

Assets/Mirror/Transports/SimpleWeb/SimpleWeb/Client/Webgl/plugin/SimpleWeb.jslib

@@ -31,14 +31,6 @@ function IsConnected(index)
 
 function Connect(addressPtr, openCallbackPtr, closeCallBackPtr, messageCallbackPtr, errorCallbackPtr)
 {
-    // fix for unity 2021 because unity bug in .jslib
-    if (typeof Runtime === "undefined")
-    {
-        // if unity doesn't create Runtime, then make it here
-        // dont ask why this works, just be happy that it does
-        var Runtime = { dynCall: dynCall }
-    }
-
     const address = UTF8ToString(addressPtr);
     console.log("Connecting to " + address);
 
@@ -52,13 +44,13 @@ function Connect(addressPtr, openCallbackPtr, closeCallBackPtr, messageCallbackP
     webSocket.onopen = function(event) 
     {
         console.log("Connected to " + address);
-        Runtime.dynCall('vi', openCallbackPtr, [index]);
+        dynCall('vi', openCallbackPtr, [index]);
     };
 
     webSocket.onclose = function(event) 
     {
         console.log("Disconnected from " + address);
-        Runtime.dynCall('vi', closeCallBackPtr, [index]);
+        dynCall('vi', closeCallBackPtr, [index]);
     };
 
     webSocket.onmessage = function(event) 
@@ -71,7 +63,7 @@ function Connect(addressPtr, openCallbackPtr, closeCallBackPtr, messageCallbackP
             var dataBuffer = new Uint8Array(HEAPU8.buffer, bufferPtr, arrayLength);
             dataBuffer.set(array);
 
-            Runtime.dynCall('viii', messageCallbackPtr, [index, bufferPtr, arrayLength]);
+            dynCall('viii', messageCallbackPtr, [index, bufferPtr, arrayLength]);
             _free(bufferPtr);
         }
         else
@@ -83,7 +75,7 @@ function Connect(addressPtr, openCallbackPtr, closeCallBackPtr, messageCallbackP
     webSocket.onerror = function(event) 
     {
         console.error('Socket Error', event);
-        Runtime.dynCall('vi', errorCallbackPtr, [index]);
+        dynCall('vi', errorCallbackPtr, [index]);
     };
 
     return index;