fix outdated/incorrect docs for `@truncate`
fix outdated/incorrect docs for `@truncate`

closes #2234

raulgrell/zig,raulgrell/zig,zig-lang/zig,zig-lang/zig,raulgrell/zig,raulgrell/zig,andrewrk/zig,raulgrell/zig,zig-lang/zig,andrewrk/zig