Update get-poetry link

Fix by python-poetry/poetry#6377 (comment)

Dockerfile

@@ -25,8 +25,8 @@ RUN apt-get update -qq \
     && rm -rf /var/cache/apt/archives/* \
     && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/* \
     && truncate -s 0 /var/log/*log
-
-RUN curl -sSL https://raw.githubusercontent.com/python-poetry/poetry/master/get-poetry.py > get-poetry.py \
+    
+RUN curl -sSL https://raw.githubusercontent.com/python-poetry/poetry/901bdf0491005f1b3db41947d0d938da6838ecb9/get-poetry.py > get-poetry.py \
     && python get-poetry.py --version 1.1.7 \
     && rm get-poetry.py
 
@@ -44,4 +44,4 @@ RUN poetry install  --no-interaction --no-ansi
 ADD . /app
 ENV DJANGO_SETTINGS_MODULE="task_manager.settings"
 
-CMD NEW_RELIC_CONFIG_FILE=newrelic.ini newrelic-admin run-program gunicorn task_manager.wsgi:application --bind 0.0.0.0:$PORT
+CMD NEW_RELIC_CONFIG_FILE=newrelic.ini newrelic-admin run-program gunicorn task_manager.wsgi:application --bind 0.0.0.0:$PORT