refactor(tvix/eval): directly return builtin tuples from macro

All invocations of the builtin macro had to previously filter through
the `builtin_tuple` function, but it's more sensible to directly
return these from the macro.

Change-Id: I45600ba84d56c9528d3e92570461c319eea595ce
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7825
Tested-by: BuildkiteCI
Reviewed-by: flokli <flokli@flokli.de>

tvix/eval/src/tests/mod.rs

@@ -48,11 +48,7 @@ fn eval_test(code_path: &str, expect_success: bool) {
     }
 
     let mut eval = crate::Evaluation::new_impure(&code, Some(code_path.into()));
-    eval.builtins.extend(
-        mock_builtins::builtins()
-            .into_iter()
-            .map(crate::builtins::builtin_tuple),
-    );
+    eval.builtins.extend(mock_builtins::builtins());
 
     let result = eval.evaluate();