✨ fix docker build

docker/spleeter.dockerfile

@@ -2,13 +2,12 @@ ARG BASE=python:3.6
 
 FROM ${BASE}
 
-ARG SPLEETER_PACKAGE=spleeter
 ARG SPLEETER_VERSION=1.5.3
 ENV MODEL_PATH /model
 
 RUN mkdir -p /model
 RUN apt-get update && apt-get install -y ffmpeg libsndfile1
 RUN pip install musdb museval
-RUN pip install ${SPLEETER_PACKAGE}==${SPLEETER_VERSION}
+RUN pip install spleeter==${SPLEETER_VERSION}
 
 ENTRYPOINT ["spleeter"]