2/n: Update wilms 06 module

[sjspielman]

Towards #850
Part of #852

This PR begins the next stages of updates for the Wilms 06 module:

• For Update the wilms 06 workflow script and GHA #852, I added the RUN_EXPLORATORY flag to the module's workflow, and I use it (so far!) to skip the 00b reference exploration notebook, and the 03 clustering notebook.
• Even so, I also updated the 03 clustering notebook to be able to run in CI - for example, we might want such steps to run on pulls but not PRs? Any thoughts there?
• I re-rendered all the sample-specific clustering notebooks, which is the MAJORITY of changes here!

Edit: Fun times with GitHub interface with this one... I could split up the notebooks into a few batches across PRs? Please let me know if that would be preferable!

[sjspielman]

Closing in favor of opening a new smaller PR, since this one is still too big!