[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 #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)                             */