[AIRFLOW-5091] Build epoch is fixed now (#5704)

We do not need monthly build epoch as we rebuild from the scratch
anyway every time new python patchlevel is released.

This happens every 1-2 months.

Dockerfile

@@ -303,10 +303,9 @@ RUN echo "Installing with extras: ${AIRFLOW_EXTRAS}."
 ARG AIRFLOW_CONTAINER_CI_OPTIMISED_BUILD="false"
 ENV AIRFLOW_CONTAINER_CI_OPTIMISED_BUILD=${AIRFLOW_CONTAINER_CI_OPTIMISED_BUILD}
 
-# By changing the CI build epoch we can force reinstalling Arflow from the current master -
-# in case of CI optimized builds (next step). Our build scripts will change the EPOCH every month normally
-# But it can also be overwritten manually by setting the AIRFLOW_CI_BUILD_EPOCH environment variable.
-ARG AIRFLOW_CI_BUILD_EPOCH=""
+# By changing the CI build epoch we can force reinstalling Arflow from the current master
+# It can also be overwritten manually by setting the AIRFLOW_CI_BUILD_EPOCH environment variable.
+ARG AIRFLOW_CI_BUILD_EPOCH="1"
 ENV AIRFLOW_CI_BUILD_EPOCH=${AIRFLOW_CI_BUILD_EPOCH}
 
 # In case of CI-optimised builds we want to pre-install master version of airflow dependencies so that

hooks/build

@@ -46,7 +46,6 @@ LAST_STEP_NAME=""
 STEP_STARTED="false"
 PYTHON_VERSION_FOR_DEFAULT_IMAGE=3.6
 AIRFLOW_CI_VERBOSE=${AIRFLOW_CI_VERBOSE:="false"}
-AIRFLOW_CI_BUILD_EPOCH=${AIRFLOW_CI_BUILD_EPOCH:=$(date +"%Y%m")}
 
 function end_step {
     if [[ "${STEP_STARTED}" != "true" ]]; then
@@ -126,7 +125,6 @@ function build_image {
         --build-arg AIRFLOW_USER="${AIRFLOW_USER}" \
         --build-arg AIRFLOW_BRANCH="${AIRFLOW_CONTAINER_BRANCH_NAME}" \
         --build-arg BUILD_NPM="${AIRFLOW_CONTAINER_BUILD_NPM}" \
-        --build-arg AIRFLOW_CI_BUILD_EPOCH="${AIRFLOW_CI_BUILD_EPOCH}" \
         --build-arg AIRFLOW_CONTAINER_CI_OPTIMISED_BUILD="${AIRFLOW_CONTAINER_CI_OPTIMISED_BUILD}" \
         --build-arg HOME="${HOME}" \
         "${DOCKER_CACHE_DIRECTIVE[@]}" \