docker tutorial fails to build

from: https://pg-auto-failover.readthedocs.io/en/main/tutorial.html

under pre-requisites:

> $ git clone https://github.com/hapostgres/pg_auto_failover
> $ cd pg_auto_failover/docs/tutorial
> $ docker compose build

fails with:

```
=> ERROR [node2 build 6/7] COPY ./src/bin/pg_autoctl/git-version.h ./src/bin/pg_autoctl/git-version.h 0.0s
=> CANCELED [node2 run 2/16] RUN apt-get update && DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends 0.0s
=> CANCELED [app 2/10] RUN apt-get update && apt-get install -y --no-install-recommends ca-certificates gnupg m 0.0s
------
> [node2 build 6/7] COPY ./src/bin/pg_autoctl/git-version.h ./src/bin/pg_autoctl/git-version.h:

114 | >>> COPY ./src/bin/pg_autoctl/git-version.h ./src/bin/pg_autoctl/git-version.h
```

there is no file `./src/bin/pg_autoctl/git-version.h` located anywhere.