fix: Use bullseye-slim as final Docker image base

`rust:1.65.0` is based on Bullseye, and at time of writing the binary
built on it does not work on Buster:

```
$ docker build -t typos . && docker run --rm -it typos typos -V
typos: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.29' not found
       (required by typos)
```

Dockerfile

@@ -3,6 +3,6 @@ WORKDIR /usr/src/typos
 COPY . .
 RUN cargo install --path .
 
-FROM debian:buster-slim
+FROM debian:bullseye-slim
 COPY --from=builder /usr/local/cargo/bin/typos /usr/local/bin/typos
 CMD ["typos"]