.gitignore: rename trace/generated-tracers.dtrace

For a while the file was called trace/generated-tracers-dtrace.dtrace
but today it's called trace/generated-tracers.dtrace.
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

.gitignore

@@ -6,7 +6,7 @@ config-target.*
 trace/generated-tracers.h
 trace/generated-tracers.c
 trace/generated-tracers-dtrace.h
-trace/generated-tracers-dtrace.dtrace
+trace/generated-tracers.dtrace
 trace/generated-events.h
 trace/generated-events.c
 libcacard/trace/generated-tracers.c