Remove setting logger name to empty string if root

[johannaengland]

Dependent on #2901.

Since Python 3.9 getLogger('root') also returns the root logger: https://github.com/python/cpython/pull/15077

Mentioned also here: https://docs.python.org/3/whatsnew/3.9.html#changes-in-the-python-api

[github-actions[bot]]

Test results

       9 files         9 suites   7m 46s :stopwatch: 3 320 tests 3 320 :heavy_check_mark: 0 :zzz: 0 :x: 6 379 runs  6 379 :heavy_check_mark: 0 :zzz: 0 :x:

Results for commit 6badf052.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 56.35%. Comparing base (b8d6d52) to head (0536ed0).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #2912 +/- ## ======================================= Coverage 56.35% 56.35% ======================================= Files 603 603 Lines 43862 43858 -4 Branches 48 48 ======================================= - Hits 24719 24718 -1 + Misses 19131 19128 -3 Partials 12 12 ```

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