corrected requirements references in backend

backend/docker/engine.Dockerfile

@@ -9,10 +9,10 @@ ENV PYTHONUNBUFFERED 1
 WORKDIR var/task/Model
 
 # Install python dependencies
-COPY ./backend/requirements/requirements.txt ./requirements.txt
+COPY ./backend/engine/requirements.txt ./requirements.txt
 # Install and clean up temp caches
 RUN pip install --upgrade pip \
-    && pip install -r backend/engine/requirements.txt && rm -rf /root/.cache
+    && pip install -r requirements.txt && rm -rf /root/.cache
 
 # Since we are not using a base AWS image, there is some additional setup required. We need to set up the runtime
 # interface client