fix(opam): mark quicktest self-test as part of the xapi-debug package

Otherwise it'd try to build it as part of another package and fail
because `rpclib.core` cannot be found.

Fixes: 1316037 ("CP-311150: test code for new library")

Signed-off-by: Edwin Török <edwin.torok@citrix.com>

Author: edwintorok

ocaml/quicktest/trace/test/dune

@@ -1,3 +1,4 @@
 (test
   (name tracetest)
+  (package xapi-debug)
   (libraries quicktest_trace quicktest_trace_rpc fmt.tty logs logs.fmt opentelemetry rpclib.core))