Change the pre-release versioning scheme and associated environment variables (#26653)

Dockerfile

@@ -42,8 +42,8 @@ RUN apt-get update && \
 FROM node:${NODE_VERSION}
 
 # Use those args to specify your own version flags & suffixes
-ARG MASTODON_VERSION_FLAGS=""
-ARG MASTODON_VERSION_SUFFIX=""
+ARG MASTODON_VERSION_PRERELEASE=""
+ARG MASTODON_VERSION_METADATA=""
 
 ARG UID="991"
 ARG GID="991"
@@ -89,8 +89,8 @@ ENV RAILS_ENV="production" \
     NODE_ENV="production" \
     RAILS_SERVE_STATIC_FILES="true" \
     BIND="0.0.0.0" \
-    MASTODON_VERSION_FLAGS="${MASTODON_VERSION_FLAGS}" \
-    MASTODON_VERSION_SUFFIX="${MASTODON_VERSION_SUFFIX}"
+    MASTODON_VERSION_PRERELEASE="${MASTODON_VERSION_PRERELEASE}" \
+    MASTODON_VERSION_METADATA="${MASTODON_VERSION_METADATA}"
 
 # Set the run user
 USER mastodon