https://github.com/juju/juju/pull/11556

## Update juju/testing dep and fix test with compare

Updates juju/testing with better HOME detection with tests that abuse env vars.
Fix cloudImageMetadataSuite.TestSupportedArchitectures array compare.

## QA steps

Run unit tests with juju-db snap installed.

## Documentation changes

N/A

## Bug reference

N/A