CompatHelper: bump compat for MLJBase to 1 for package docs, (keep existing compat)

[github-actions]

This pull request changes the compat entry for the MLJBase package from 0.19, 0.20, 0.21 to 0.19, 0.20, 0.21, 1 for package docs.
This keeps the compat entries for earlier versions.

Note: I have not tested your package with this new compat entry.
It is your responsibility to make sure that your package tests pass before you merge this pull request.

[github-actions]

Pull Request Test Coverage Report for Build 6306281191

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 96.655%

---

Totals
Change from base Build 6022939932:	0.0%
Covered Lines:	838
Relevant Lines:	867

---

💛 - Coveralls

[codecov]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (627d945) 96.65% compared to head (95f62bd) 96.65%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #100   +/-   ##
=======================================
  Coverage   96.65%   96.65%           
=======================================
  Files          11       11           
  Lines         867      867           
=======================================
  Hits          838      838           
  Misses         29       29           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.