doc: sml: Mark promiscuous mode as supported

This is now a supported feature.

Signed-off-by: Chaitanya Tata <[email protected]>
(cherry picked from commit c69c6d9)

Author: krish2718

doc/nrf/releases_and_maturity/software_maturity.rst

@@ -1307,7 +1307,7 @@ The following table indicates the software maturity levels of the support for ea
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-        - Experimental\ :sup:`2`
+        - Supported\ :sup:`2`
         - --
         - --
         - --