add python version in Dockerfile and change PYTHONUNBUFFERED value to 1

Dockerfile

@@ -1,4 +1,4 @@
-FROM python:alpine
+FROM python:3.10-alpine
 
 WORKDIR /bot
 
@@ -6,7 +6,7 @@ COPY . .
 
 RUN pip install -r requirements.txt
 
-ENV PYTHONUNBUFFERED='a'
+ENV PYTHONUNBUFFERED=1
 
 ENTRYPOINT [ "python" ]