fix: remove Dockerfile spaceone-core install command

Signed-off-by: ImMino <mino@megazone.com>

Author: ImMin5

Dockerfile

@@ -11,7 +11,7 @@ RUN apt update && apt upgrade -y
 COPY pkg/*.txt ${PKG_DIR}/
 RUN pip install --upgrade pip && \
     pip install --upgrade -r ${PKG_DIR}/pip_requirements.txt && \
-    pip install --upgrade --pre spaceone-core spaceone-api
+    pip install --upgrade spaceone-api
 
 COPY src ${SRC_DIR}