developer_guides: debugability: probes: Fix misleading statement

The statement about enabling a single probe point for buffer #7 was
misleading.

Signed-off-by: Jyri Sarha <jyri.sarha@intel.com>

Author: jsarha

developer_guides/debugability/probes/index.rst

@@ -124,7 +124,7 @@ the last stage of extraction.
      - Add probe points via the ``debugfs`` "probe_points" entry in ``/sys/kernel/debug/sof``
 
 
-   For example, to add a buffer with 7 probe points:
+   For example, to add buffer 7 with a probe point:
 
    .. code-block:: bash