Fix: correct RHEL range for kmem_cache_free define

Fix: correct RHEL range for kmem_cache_free define

When compiling against RHEL 8.5 kernels, lttng-modules builds fail
with the following error:

```
lttng-modules/src/probes/../../include/lttng/tracepoint-event-impl.h:133:6: error: conflicting types for ‘trace_kmem_
cache_free’; have ‘void(long unsigned int,  const void *)’
```

The original range was introduced in commit
89d917153fc52c1e5b0ddabf8ee078897656b263 which tested against RHEL 8.6
and not RHEL 8.5.

Change-Id: Icff98c15415ce8e1e95a10974cd65ed6e84cd00a
Signed-off-by: Kienan Stewart <kstewart@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>