Update etherpad to v2.2.6

This appears to be a small update compared to other recent updates. In
particular the dockerfile has not changed and neither have the
settings.json files. The changelog can be found here:

  https://github.com/ether/etherpad-lite/blob/v2.2.6/CHANGELOG.md

The only notable update there is that pads can be deleted by their
creators. I suspect this is a noop for us since we don't do
authenticated access, but we should check with a held node.

Change-Id: I4e935828912d004eb7694e981926557db8b26e56

docker/etherpad/Dockerfile

@@ -42,7 +42,7 @@ RUN export DEBIAN_FRONTEND=noninteractive; \
     rm -rf /var/lib/apt/lists/*
 RUN npm install -g pnpm@9.0.4
 RUN git clone https://github.com/ether/etherpad-lite ${EP_DIR}
-RUN git checkout v2.2.5
+RUN git checkout v2.2.6
 RUN pnpm install
 RUN pnpm run build:ui
 
@@ -149,7 +149,7 @@ USER etherpad
 
 RUN git clone https://github.com/ether/etherpad-lite ${EP_DIR}
 WORKDIR "${EP_DIR}"
-RUN git checkout v2.2.5
+RUN git checkout v2.2.6
 
 FROM build AS development
 ARG ETHERPAD_PLUGINS

zuul.d/docker-images/etherpad.yaml

@@ -11,7 +11,7 @@
           repository: opendevorg/etherpad
           tags:
             - latest
-            - v2.2.5
+            - v2.2.6
           build_args:
             - EP_GID=5001
     files: &etherpad_files