Drop duplicate linking to libvncserver.

Summary:
The duplicate link may also be missing necessary -L flags,
so it causes linker errors when libvncserver is installed
in unusual places (while ${LIBVNCSERVER_LIBRARIES} DTRT).

Reviewers: sitter, apol, ltoscano, heikobecker

Reviewed By: sitter

Differential Revision: https://phabricator.kde.org/D5018

krfb/CMakeLists.txt

@@ -78,7 +78,6 @@ add_executable (krfb
 
 target_link_libraries (krfb
                        krfbprivate
-                       vncserver
                        ${JPEG_LIBRARIES}
                        ${X11_Xext_LIB}
                        ${X11_X11_LIB}