cleanup ROTATE_BACKUPS_VERSION build arg that for some reason does not work

.gitea/workflows/build-and-publish.yaml

@@ -42,4 +42,3 @@ jobs:
         build_args: |
           PYTHON_VERSION=3
           ALPINE_VERSION=3.18
-          ROTATE_BACKUPS_VERSION=8.1

Dockerfile

@@ -1,14 +1,12 @@
 
 ARG PYTHON_VERSION=3
 ARG ALPINE_VERSION=3.18
-ARG ROTATE_BACKUPS_VERSION=8.1
 
 FROM python:${PYTHON_VERSION}-alpine${ALPINE_VERSION}
 
 RUN apk update && apk add less
 
-# RUN pip install rotate-backups==8.1
-RUN pip install rotate-backups==${ROTATE_BACKUPS_VERSION}
+RUN pip install rotate-backups==8.1
 
 RUN mkdir /data