Broken link in "Templates generator" docs page

[yousefmoazzam]

The following github link in yaml_generator.rst is outdated and returns a 404 when visiting it in the deployed docs:

httomo-backends/docs/source/utilities/yaml_generator.rst

Line 5 in a34bf58

:ref:`backends_content` can be generated automatically using the YAML generator tool `provided <https://github.com/DiamondLightSource/httomo/tree/main/scripts/yaml_templates_generator.py>`_ in the Github repo.

The link was valid when the yaml_templates_generator.py script was in httomo, but that script has since been moved to httomo-backends.