sim: Remove the ProbePoints namespace

This namespace has gone through the deprecation period
and can now be removed.

Change-Id: Iddf30ea24a579cf5a94d6217c1d015a0c68d68d0
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/67371
Reviewed-by: Richard Cooper <richard.cooper@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>

src/sim/probe/mem.hh

@@ -46,7 +46,6 @@
 namespace gem5
 {
 
-GEM5_DEPRECATED_NAMESPACE(ProbePoints, probing);
 namespace probing
 {
 

src/sim/probe/pmu.hh

@@ -45,7 +45,6 @@
 namespace gem5
 {
 
-GEM5_DEPRECATED_NAMESPACE(ProbePoints, probing);
 namespace probing
 {
 

src/sim/probe/probe.hh

@@ -86,7 +86,6 @@ struct ProbeListenerObjectParams;
  * common instrumentation interface for devices such as PMUs that have
  * different implementations in different ISAs.
  */
-GEM5_DEPRECATED_NAMESPACE(ProbePoints, probing);
 namespace probing
 {
 /* Note: This is only here for documentation purposes, new probe