Fix didkit paths in CI

[clehner]

Fix #111 caching of Rust build artifacts in CI.

Full run, no cache: https://github.com/spruceid/didkit/runs/2142681378 45m 49s
Subsequent run, with caching: https://github.com/spruceid/didkit/runs/2143040544: failed for disk space reasons. Looks like we have to free up more space to make room for the larger cache file.

Cache size which previously was ~263 MB (probably containing just the cargo registry data); is now up to ~2141 MB (step:4:23).

[wyc]

Hi @clehner, is this ready for review?

[clehner]

@wyc I'm not sure how to proceed here. I believe the change does what it is supposed to do, enabling caching the build artifacts (target/), however it was causing test failure due to running out of space because of the size of the data to cache. I experimented with deleting existing files from the CI environment, to free up space (in order to hold the cache data), in #109, but that added more time to the run to delete all those files. I recall that the time deleting the files to free up space was close to or greater than the time saved by caching the build artifacts, so I stopped pursuing it after other changes (#110, #116) stopped the out-of-space issue (#108) that we were seeing around that time. The CI run here currently takes an hour, so reducing that could be good; I could look into these changes and #109 again if that would be useful; otherwise I think this PR could be closed or changed to simply remove the incorrectly-referenced paths.

[bumblefudge]

@clehner will open an issue for tracking purposes