ci: use the runner image's node instead of setup-node, which downloaded it again on every run

tools/cut.zig

@@ -1659,9 +1659,9 @@ fn toolchainParity(ctx: *Ctx) ![]const u8 {
         return CheckFailed;
     };
 
-    // `node --version` prints `v24.19.0`; the workflow pins the number the way
-    // setup-node takes it, without the `v`. `npm --version` and `zig version`
-    // print the bare number already.
+    // `node --version` prints `v24.19.0`; the workflow pins the bare number,
+    // without the `v`. `npm --version` and `zig version` print the bare number
+    // already.
     try assertVersion(ctx, "node", &.{ "node", "--version" }, "v", pins.node);
     try assertVersion(ctx, "npm", &.{ "npm", "--version" }, "", pins.npm);