Remove torch GPU dependencies from the Docker.full image (#665)

By using `pip install torch --index-url https://download.pytorch.org/whl/cpu`
instead of `pip install torch` we can specify we want to install a CPU-only version
of PyTorch without any GPU dependencies. This reduces the size of the Docker image
from 7.32 GB to 1.62 GB

.devops/full.Dockerfile

@@ -6,7 +6,8 @@ RUN apt-get update && \
     apt-get install -y build-essential python3 python3-pip
 
 RUN pip install --upgrade pip setuptools wheel \
-    && pip install numpy requests sentencepiece torch tqdm
+    && pip install numpy requests sentencepiece tqdm \
+    && pip install torch --index-url https://download.pytorch.org/whl/cpu
 
 WORKDIR /app