mem-cache: Remove the Encoder namespace

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

Change-Id: Iabe3b61eb2409a10c582ab1f1c26abc649c1646a
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/67355
Reviewed-by: Richard Cooper <richard.cooper@arm.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/mem/cache/compressors/encoders/base.hh

@@ -38,7 +38,6 @@ namespace gem5
 
 namespace compression
 {
-GEM5_DEPRECATED_NAMESPACE(Encoder, encoder);
 namespace encoder
 {
 

src/mem/cache/compressors/encoders/huffman.cc

@@ -37,7 +37,6 @@ namespace gem5
 
 namespace compression
 {
-GEM5_DEPRECATED_NAMESPACE(Encoder, encoder);
 namespace encoder
 {
 

src/mem/cache/compressors/encoders/huffman.hh

@@ -44,7 +44,6 @@ namespace gem5
 
 namespace compression
 {
-GEM5_DEPRECATED_NAMESPACE(Encoder, encoder);
 namespace encoder
 {