build-aux: Remove check for x11-xcb

We're no longer building QT with libX11/XLib, so it doesn't make sense
to check for the x11-xcb package.

build-aux/m4/bitcoin_qt.m4

@@ -355,7 +355,6 @@ AC_DEFUN([_BITCOIN_QT_FIND_STATIC_PLUGINS],[
          PKG_CHECK_MODULES([QTFB], [Qt5FbSupport], [QT_LIBS="-lQt5FbSupport $QT_LIBS"])
                 fi
        if test "x$TARGET_OS" = xlinux; then
-         PKG_CHECK_MODULES([X11XCB], [x11-xcb], [QT_LIBS="$X11XCB_LIBS $QT_LIBS"])
          PKG_CHECK_MODULES([QTXCBQPA], [Qt5XcbQpa], [QT_LIBS="$QTXCBQPA_LIBS $QT_LIBS"])
        elif test "x$TARGET_OS" = xdarwin; then
          PKG_CHECK_MODULES([QTCLIPBOARD], [Qt5ClipboardSupport], [QT_LIBS="-lQt5ClipboardSupport $QT_LIBS"])