cmd/bundle: remove summary --show-full-config (#5241)

## Summary
- Removes the hidden `bundle summary --show-full-config` flag and its
handler from `cmd/bundle/summary.go`.
- Deletes the corresponding
`acceptance/bundle/summary/show-full-config/` test directory.
- The flag has been superseded by `bundle debug list-targets`, which
already covers the same use case.

## Test plan
- [ ] `./task build` succeeds.
- [ ] `./task test` passes; no acceptance tests reference
`--show-full-config`.
- [ ] `databricks bundle summary --show-full-config` now errors with
"unknown flag" as expected.
- [ ] `databricks bundle debug list-targets` continues to work as the
replacement.

Author: pavloKozlov