Remove env variable

`RAGE_PATCH_AR_POOL` is enabled by default since v1.10

Author: rsamoilov

frameworks/Ruby/rage/rage.dockerfile

@@ -8,7 +8,6 @@ RUN bundle install --jobs=8
 COPY . /rage
 
 ENV RUBY_YJIT_ENABLE=1
-ENV RAGE_PATCH_AR_POOL=1
 ENV BUNDLE_FORCE_RUBY_PLATFORM=true
 
 CMD bundle exec rage s -b 0.0.0.0 -p 8080 -e production