Remove configuration for non-existant schema tests

[braingram]

The current pyproject.toml enables asdf schema tests for 2 directories that do not exist:

jwst/pyproject.toml

Lines 226 to 228 in 77c4966

	asdf_schema_tests_enabled = true
	asdf_schema_validate_default = false
	asdf_schema_root = "jwst/transforms/resources/schemas jwst/datamodels/schemas"

As the directories do not exist, no tests are run.

These could have been disabled in: #7439 which moved the schemas to stdatamodels (where they are tested)

This PR removes the configuration in pyproject.toml that enables the asdf schema tests.

Checklist for maintainers

• added entry in CHANGES.rst within the relevant release section
• updated or added relevant tests
• updated relevant documentation
• added relevant milestone
• added relevant label(s)
• ran regression tests, post a link to the Jenkins job below.
  How to run regression tests on a PR
• Make sure the JIRA ticket is resolved properly

[braingram]

As seen in the py310 CI job. With this PR 3343 tests are being run:
https://github.com/spacetelescope/jwst/actions/runs/8297231789/job/22707918174?pr=8366
on main the same number of tests were run for this job:
https://github.com/spacetelescope/jwst/actions/runs/8296966128/job/22707041209#step:10:118

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 56.30%. Comparing base (2fb073e) to head (4928291).
Report is 33 commits behind head on master.

❗ Current head 4928291 differs from pull request most recent head edf231b. Consider uploading reports for the commit edf231b to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #8366       +/-   ##
===========================================
- Coverage   75.31%   56.30%   -19.01%     
===========================================
  Files         474      390       -84     
  Lines       38965    38889       -76     
===========================================
- Hits        29345    21895     -7450     
- Misses       9620    16994     +7374     

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[emolter]

looks good to me