DolphinQt: Remove workaround for Qt6.3 bug on Linux

Source/Core/DolphinQt/Main.cpp

@@ -140,16 +140,6 @@ int main(int argc, char* argv[])
   }
 #endif
 
-#ifdef __linux__
-  // Qt 6.3+ has a bug which causes mouse inputs to not be registered in our XInput2 code.
-  // If we define QT_XCB_NO_XI2, Qt's xcb platform plugin no longer initializes its XInput
-  // code, which makes mouse inputs work again.
-  // For more information: https://bugs.dolphin-emu.org/issues/12913
-#if (QT_VERSION >= QT_VERSION_CHECK(6, 3, 0))
-  setenv("QT_XCB_NO_XI2", "1", true);
-#endif
-#endif
-
   QCoreApplication::setOrganizationName(QStringLiteral("Dolphin Emulator"));
   QCoreApplication::setOrganizationDomain(QStringLiteral("dolphin-emu.org"));
   QCoreApplication::setApplicationName(QStringLiteral("dolphin-emu"));