Broken link in "Templates generator" docs page

The following github link in `yaml_generator.rst` is outdated and returns a 404 when visiting it in the deployed docs: https://github.com/DiamondLightSource/httomo-backends/blob/a34bf5802fc541ef5a0c541377b000ce596882aa/docs/source/utilities/yaml_generator.rst?plain=1#L5

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