Fix: Removed duplicated dockerfile path

Author: SloCompTech

hooks/build

@@ -10,5 +10,4 @@ docker build \
     --build-arg BUILD_DATE=`date -u +"%Y-%m-%dT%H:%M:%SZ"` \
     --build-arg VCS_REF=$SOURCE_COMMIT \
     --build-arg VCS_SRC="https://github.com/SloCompTech/docker-openvpn/commit/$SOURCE_COMMIT"
-    -f $DOCKERFILE_PATH \
     -t $IMAGE_NAME .