config-linux: add a note about the dropped intelRdt parameters

Add a note that documents the removal of intelRdt.enableCMT and
intelRdt.enableMBM parameters.

Signed-off-by: Markus Lehtonen <markus.lehtonen@intel.com>

Author: marquiz

config-linux.md

@@ -779,6 +779,12 @@ The following rules on parameters MUST be applied:
   group fails (e.g. the maximum number of MON groups is reached) the runtime MUST
   return an error.
 
+> **NOTE:** The `enableCMT` and `enableMBM` parameters, available in runtime-spec versions v1.1.0 through v1.2.1, were
+> replaced with a unified `enableMonitoring` parameter in v1.3.0. Their semantics were loosely defined and there were
+> no known implementations. More critically, these parameters were problematic as hardware does not support selective
+> enabling of individual monitoring features. This scheme also made it unnecessarily complex to add support for new
+> monitoring features, without providing any recognized benefits.
+
 ### Example
 
 Consider a two-socket machine with: