mod(event): do not care about enum declarations

The union type can not be constructed with declarations anyway:
`error: reified unions must have no decls`; meaning there is no point in
even trying to do so.

src/event.zig

@@ -92,7 +92,7 @@ pub fn mergeTaggedUnions(comptime A: type, comptime B: type) type {
         .layout = .auto,
         .tag_type = Event,
         .fields = fields[0..],
-        .decls = if (decls.len != 0) decls[0..] else &.{},
+        .decls = &.{},
     } });
 }