[util] Add new "Zusi 3" exe filename

In addition to the legacy "ZusiSim.exe" executable, the recent 3.5
release added a 64-bit "ZusiSim.64.exe" executable. This is now the
default executable when launching the game in Steam. The game is
unplayable without this option, so update the regex for Zusi 3.

Fixes doitsujin#3250.

src/util/config/config.cpp

@@ -462,7 +462,7 @@ namespace dxvk {
       { "d3d9.allowDiscard",                "False" },
     }} },
     /* ZUSI 3 - Aerosoft Edition                  */
-    { R"(\\ZusiSim\.exe$)", {{
+    { R"(\\ZusiSim(\.64)?\.exe$)", {{
       { "d3d9.noExplicitFrontBuffer",       "True" },
     }} },
     /* GTA IV (NVAPI)                             */