Fix CI

[WillB97]

Use repo version of sr-tools

[PeterJCLaw]

I appreciate the desire here, however using the development version of the tools has a number of consequences -- most notably that still-in-development behaviours could end up committed to the inventory repo and thus foisted upon users who may not have (or even be able) to install that version of the tooling.

(I'm also slightly surprised that this works -- the reason that we've not published a new version of the tools is that their build stack is somewhat broken)

[RealOrangeOne]

I'm afraid I agree with Peter here. Pinning like this is likely to cause us more headaches in future. Even if what's there now is stable enough for us to use, it might not always be true (although IMO main should still be reasonably stable, even if not "production-grade").

I see 3 possible ways forward:

1. Fix sr.tools upstream, ship a release, which should then fix CI here (preferred).
2. Pin to a specific commit. Sure, it's far from ideal, but at least this way we're at a stable-ish version which will more reliably work, even if we do this whilst going with Option 1.
3. Just disable CI. Ignoring CI errors (and communicating that's what people should do) is objectively worse than having no CI.

[RealOrangeOne]

I like this totally temporary solution.