Predeclared identifiers are not recognized

[rillig]

https://github.com/NetBSD/src/blob/e133a890f44e4a1356c621997c585b29e14fc72c/distrib/sets/fmt-list

The identifier assert is marked as unknown, even though it should be known. In the Settings, I configured a Lua 5.3.5 environment as the default environment. The Lua 5.3 manual lists assert as one of the predefined functions.