base: Remove the Debug namespace

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

Change-Id: I4241501f3683c1daa8554693cba7aa2c022db130
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/67360
Reviewed-by: Richard Cooper <richard.cooper@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>

build_tools/debugflaghh.py

@@ -82,7 +82,6 @@ code(
 namespace gem5
 {
 
-GEM5_DEPRECATED_NAMESPACE(Debug, debug);
 namespace debug
 {
 

src/base/debug.cc

@@ -52,7 +52,6 @@
 namespace gem5
 {
 
-GEM5_DEPRECATED_NAMESPACE(Debug, debug);
 namespace debug
 {
 

src/base/debug.hh

@@ -53,7 +53,6 @@
 namespace gem5
 {
 
-GEM5_DEPRECATED_NAMESPACE(Debug, debug);
 namespace debug
 {