update recipe v1 README; mark as fully supported

[h-vetinari]

The readme for the v1 example recipe currently says (my bold)

The v1 recipe format is fully functional when built with rattler-build, but is not yet fully supported by conda-forge's automation.

That was true in the second half of 2024 (f47d93e), but in the meantime, I think we can take off the "not fully supported" label.

CC @conda-forge/core

[conda-forge-admin]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR () and found it was in an excellent condition.

[github-actions]

Hi! This is the staged-recipes linter and I found some lint.

File-specific lints and/or hints:

• recipes/example-v1/README.md:
  • lints:
    • Please put your recipe in its own directory in the recipes/ directory as recipe/<name of feedstock>/<your recipe file>.yaml.