fix: build Docker dev containers

[froger]

Hi,
This PR is to fix the Docker dev container build.

I got the following issues while building:

 => ERROR [wiki 2/3] RUN apt-get update &&     apt-get install -y bash curl git python make g++ nano openssh-server gnupg &&     mkd  5.7s
------
 > [wiki 2/3] RUN apt-get update &&     apt-get install -y bash curl git python make g++ nano openssh-server gnupg &&     mkdir -p /wiki:
[...]
#0 4.439 Package python is not available, but is referred to by another package.
#0 4.439 This may mean that the package is missing, has been obsoleted, or
#0 4.439 is only available from another source
#0 4.439 However the following packages replace it:
#0 4.439   python-is-python3 2to3
#0 4.439 
#0 4.457 E: Package 'python' has no installation candidate

I tested to build the container, install the dependancies (yarn install), and then a yarn dev. This seems OK now.

Thanks,