chore: switch datalad-core dependency to released version

[mslw]

With datalad-core v0.1.1 now on PyPi and containing the following fixes (copied from datalad-core changelog for v0.1.1):

annex-lookup in Annex() now supports secondary worktrees
git-annex:
    bump version to include fix non-symlink repo handling

there are no more reasons to be using a version from GitHub as dependency. Closes #94

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.27%. Comparing base (c5d4359) to head (bb1090b).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #100      +/-   ##
==========================================
+ Coverage   84.72%   93.27%   +8.54%     
==========================================
  Files          29       29              
  Lines        1159     1159              
  Branches      106      106              
==========================================
+ Hits          982     1081      +99     
+ Misses        136       50      -86     
+ Partials       41       28      -13     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.