Correct sparse decoration motive example

[gemshrine]

Fixes #1458

The sparse-decoration motive presented an if > @ application with no void arguments as a correct example. The lint intentionally reports that shape as sparse, so the documentation contradicted the rule and its own fixture.

The example now gives the formation a free void argument, which makes the decoration non-sparse under the lint's definition. The duplicate standalone example was removed so the motive has one unambiguous correct example for this case.

Verification:

• git diff --check