fix: remove unused env

Author: clemak27

Containerfile

@@ -7,8 +7,6 @@ COPY build.sh /tmp/build.sh
 COPY plasma.sh /tmp/plasma.sh
 COPY cosign.pub /tmp/cosign.pub
 
-ARG RELEASE_VERSION
-
 RUN mkdir -p /var/lib/alternatives
 
 RUN /tmp/build.sh && \