Readd submodule

[alamb]

• Targets PR Add sqlite test files, progress bar, and automatic postgres container management into sqllogictests apache/datafusion#13936

The submodule wasn't working for me for some reason. I ran these commands locally to create this PR

(venv) andrewlamb@Andrews-MacBook-Pro-2:~/Software/datafusion2$ git rm datafusion-testing
rm 'datafusion-testing'
(venv) andrewlamb@Andrews-MacBook-Pro-2:~/Software/datafusion2$ git submodule add --force https://github.com/apache/datafusion-testing.git
Reactivating local git directory for submodule 'datafusion-testing'
(venv) andrewlamb@Andrews-MacBook-Pro-2:~/Software/datafusion2$ git add datafusion-testing/
(venv) andrewlamb@Andrews-MacBook-Pro-2:~/Software/datafusion2$ git commit -a -m 'Readd submodule'
[alamb/fix_datafusion-testing 5230c8bfc] Readd submodule
 1 file changed, 1 insertion(+), 1 deletion(-)
 mode change 100755 => 160000 datafusion-testing

I don't know what mode change 100755 => 160000 datafusion-testing means, but it seems like the github UI suggests git can now recognize this directory as a submodule: