chore: arch: Remove XArch exception class

XArch no longer contains any extra functionality in addition to what
std::runtime_error nor it signifies a particular type of error.
based-on: 5b991692af
ported-by: sithlord48

src/lib/platform/XWindowsScreen.cpp

@@ -104,7 +104,7 @@ XWindowsScreen::XWindowsScreen(
   if (!disableXInitThreads) {
     // initializes Xlib support for concurrent threads.
     if (XInitThreads() == 0)
-      throw XArch("XInitThreads() returned zero");
+      throw std::runtime_error("XInitThreads() returned zero");
   } else {
     LOG((CLOG_DEBUG "skipping XInitThreads()"));
   }