pixi init --pyproject snippit in the how to install user guide deprecated

[Tjalling-dejong]

HydroMT version checks

• I have checked that the issue still exists on the latest versions of the docs on main here

Kind of issue

Docs are wrong

Location of the documentation

here

In the 'Installing HydroMT in a python environment' section, the first snippet: $ pixi init --pyproject

Documentation problem

calling init --pyproject is deprecated.

Suggested fix for documentation

call should change to pixi init --format pyproject