PhpDoc: Fix two misspelled class references
Summary: Markup is `@{class:foo}`, not `{@class:foo}`.
Test Plan: Look at other PhpDoc comments. Optionally, run `./bin/diviner generate` (I did not).
Reviewers: O1 Blessed Committers, valerio.bozzolan
Reviewed By: O1 Blessed Committers, valerio.bozzolan
Subscribers: tobiaswiese, valerio.bozzolan, Matthew, Cigaryno
Differential Revision: https://we.phorge.it/D26508