perf script: Fix broken include in Context.xs

perf script: Fix broken include in Context.xs

765532c8 (perf script: Finish the rename from trace to script,
2010-12-23) made a mistake during find-and-replace replacing
"../../../util/trace-event.h" with "../../../util/script-event.h", a
non-existent file.  Fix this include.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/1373364033-7918-3-git-send-email-artagnon@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>