Data Quality Tool text update

[KDuerden]

These changes update the text and images in the DQT guidance. As this is in the non-normative section of the documentation site, these changes can be made live without needing to go through the Standard governance process.

[KDuerden]

The screenshots are clear and well indicated by the text. In future patches, I recommend we consider labeling these for further clarity e.g. "Figure 1", "Figure 2" etc but this is absolutely optional and the page renders and reads very well as it is.

This is a good idea, we should do some housekeeping across the board for this!

[mariongalley]

This looks good to me in the live guidance https://standard.threesixtygiving.org/en/latest/guidance/data-quality/

Possibly a few spacing/formatting things could be improved but I'm very happy to share this as is