starting from `~` instead of using the whole path

to prevent issues when interacting with the repository both from within
the container and outside the container, due to permissions not being
correct

in `Dockerfile`, because the `updateRemoteUserUID` setting of the
devcontainer does not change the `GID` of the `containerUser`
dynamically to the one of the host user if the group exists in the
container already microsoft/vscode-remote-release#2402.

In our case the `containerUser` is set to `bitbots`, because it
automatically uses the last `USER` instruction from the `Dockerfile` and
the `remoteUser` inherits from `containerUser`.

For reference see: microsoft/vscode-remote-release#1155

as with upgrade to jazzy or packages floating point handling seems to
have changed slightly