Fixed 8.10 not building

[Soupstraw]

Description

There seems to be a problem with some Inject constraints in ExecSpecRule. It looks like 8.10 can derive some identity constraints from the Inject a a instance, but GHC 9 complains about overlapping instances.

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• New tests are added if needed and existing tests are updated
• When applicable, versions are updated in .cabal and CHANGELOG.md files according to the
  versioning process.
• The version bounds in .cabal files for all affected packages are updated. If you change the bounds in a cabal file, that package itself must have a version increase. (See RELEASING.md)
• All visible changes are prepended to the latest section of a CHANGELOG.md for the affected packages. New section is never added with the code changes. (See RELEASING.md)
• Code is formatted with fourmolu (use scripts/fourmolize.sh)
• Cabal files are formatted (use scripts/cabal-format.sh)
• hie.yaml has been updated (use scripts/gen-hie.sh)
• Self-reviewed the diff

[teodanciu]

Looks good to me, let's maybe check that it passes for all the builds before merging, since at the moment this check is not correct in CI.