Drop manual bundler installation (#1038)

Since bundler 2.3.0 (2021-12-21), it automatically takes care of installing & using the version specified in `Gemfile.lock`.

Author: davidtaylorhq

image/base/Dockerfile

@@ -156,8 +156,7 @@ ARG DISCOURSE_BRANCH=main
 
 # Discourse specific bits
 RUN install -dm 0755 -o discourse -g discourse /var/www/discourse &&\
-    sudo -u discourse git clone --branch $DISCOURSE_BRANCH --filter=tree:0 https://github.com/discourse/discourse.git /var/www/discourse &&\
-    gem install bundler --conservative -v $(awk '/BUNDLED WITH/ { getline; gsub(/ /,""); print $0 }' /var/www/discourse/Gemfile.lock)
+    sudo -u discourse git clone --branch $DISCOURSE_BRANCH --filter=tree:0 https://github.com/discourse/discourse.git /var/www/discourse
 
 FROM discourse_slim AS discourse_web_only
 ENV RAILS_ENV=production

templates/web.template.yml

@@ -180,8 +180,6 @@ run:
       cd: $home
       hook: web
       cmd:
-        # install bundler version to match Gemfile.lock
-        - gem install bundler --conservative -v $(awk '/BUNDLED WITH/ { getline; gsub(/ /,""); print $0 }' Gemfile.lock)
         - find $home ! -user discourse -exec chown discourse {} \+
 
   - exec: