fix: wipe toml dfn dir before regenerating mf6 module

[wpbonelli]

Delete all the TOMLs before recreating them from DFNs otherwise unwanted TOML components can remain

[codecov]

Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.4%. Comparing base (556c088) to head (e5966f6).
⚠️ Report is 140 commits behind head on develop.

Files with missing lines	Patch %	Lines
flopy/mf6/utils/generate_classes.py	0.0%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2730      +/-   ##
===========================================
+ Coverage     55.5%    72.4%   +16.9%     
===========================================
  Files          644      674      +30     
  Lines       124135   130626    +6491     
===========================================
+ Hits         68947    94641   +25694     
+ Misses       55188    35985   -19203     

Files with missing lines	Coverage Δ
flopy/mf6/utils/generate_classes.py	17.3% <0.0%> (-0.3%)	⬇️

... and 569 files with indirect coverage changes

🚀 New features to boost your workflow:

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