PHPDoc: Correct syntax of variadic function params
Summary: PHPDoc standardized syntax for variadic function parameters in https://github.com/phpDocumentor/phpDocumentor/issues/629. Thus follow that syntax.
Test Plan:
* Check that Phorge docs still render as before: grep for `...` within src/applications/diviner, see that the only result writes and does not read
* Run `./bin/diviner generate --clean`, see that "Loading Objects" section on http://phorge.localhost/book/dev/class/LiskDAO/ looks the same before and after
* Run static code analysis, get no more parse errors which mention `...`
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/D25980