EPIC: gha comparison logic

When the GHA is ran, it is not taking into account the comparisons like it should. The below tickets will correct this logic error.

~TODO - the above logic needs to be changed a bit to reflect comparing to the common ancestor commit of the base branch, NOT the default branch. In order to do this, we will need to be grabbing the base branch from the git info and saving that as well as default branch info per commit. These tickets are on hold until this is thought out a bit further and the corresponding tickets are modified**~ EDIT: we are only comparing to the last scan of the default branch. We are trying to answer the question "how does my commit affect the current accessibility of the default branch?" so comparing to the last commit is the correct way to answer thing. No need to find a common ancenstor

```[tasklist]
### Tasks
- [ ] https://github.com/dequelabs/jazzband/issues/780
- [ ] https://github.com/dequelabs/walnut/issues/7236
- [ ] https://github.com/dequelabs/axe-devhub-action/issues/134
- [ ] https://github.com/dequelabs/jazzband/issues/1218
- [ ] https://github.com/dequelabs/jazzband/issues/1219
```