kmousetool: remove unused header file

Inclusion of `X11/extensions/xtestext1.h` was causing problems when
building with clang (see [1]) due to it's use of register keyword. Since
the header is not actually used just remove it.

[1]: https://mirror.git.trinitydesktop.org/gitea/TDE/tdeaccessibility/pulls/39

Signed-off-by: Alexander Golubev <fatzer2@gmail.com>
(cherry picked from commit 1565cb42d3)

kmousetool/kmousetool/kmousetool.cpp

@@ -26,7 +26,6 @@
 #include <tdeconfig.h>
 #include <X11/Intrinsic.h>     /* Intrinsics Definitions*/
 #include <X11/StringDefs.h>    /* Standard Name-String definitions*/
-#include <X11/extensions/xtestext1.h>    /* Standard Name-String definitions*/
 #include <X11/extensions/XTest.h>    /* Standard Name-String definitions*/
 #include <kdialog.h>
 #include <tdelocale.h>