Increase cURL timeout in Dockerfile

Hi,

The `--max-time` value in the Dockerfile seems unnecessarily low and can cause the build to fail (even on a gigabit connection it seems).

```
RUN curl --silent \
--connect-timeout 5 \
--max-time 10 \
--retry 5 \
--retry-delay 0 \
--retry-max-time 40 \
--output beaker.tar.gz \
"https://beaker.org/api/v3/release/cli?os=linux&arch=amd64&version=${BEAKER_VERSION}" \
&& tar -zxf beaker.tar.gz -C /usr/local/bin/ ./beaker \
&& rm beaker.tar.gz
```

It builds successfully after increasing this to 100.