TST: Remove broken test for deprecated functionality
Registering converters by default on import is deprecated since #28722.

The test did not fail as the subprocess call contains errors in the python code. Specifically, the code is in double and single quotes. This means that the python code passed to the subprocess call is never actually excecuted. Python in the subprocess is called to "excecute" a string. This is will simply finish with exit code 0 as there is nothing to do basically.
Additonally, the test code contains a stray closing bracket at the end which would make the code fail if it was excecuted. 

- [ ] closes #xxxx
- [ ] tests added / passed
- [x] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry

can u fix the test instead  How would you want this test fixed? There is a test for registering the converters explicitly. I don't know what case still needs to be tested with this after converters are no longer automatically registered. this is a test that is using a sub process so it's different - it makes sure that we are not corrupting things in import  As far as my understanding went, there is nothing converter related done on import anymore. That's why I thought the test is no longer needed. But you are suggesting that something about the imports still needs to have a test. 
I probably don't have a deep enough understanding of what is done there then. So somebody who knows this better should probably look at this to fix it properly. thanks @theOehrly 