std.crypto.kangarootwelve: disable flaky test

tracked by #30676

lib/std/crypto/kangarootwelve.zig

@@ -1339,6 +1339,11 @@ test "KT128 sequential and parallel produce same output for small inputs" {
 }
 
 test "KT128 sequential and parallel produce same output for large inputs" {
+    if (true) {
+        // https://codeberg.org/ziglang/zig/issues/30676
+        return error.SkipZigTest;
+    }
+
     const allocator = std.testing.allocator;
     const io = std.testing.io;
 
@@ -1374,6 +1379,11 @@ test "KT128 sequential and parallel produce same output for large inputs" {
 }
 
 test "KT128 sequential and parallel produce same output for many random lengths" {
+    if (true) {
+        // https://codeberg.org/ziglang/zig/issues/30676
+        return error.SkipZigTest;
+    }
+
     const allocator = std.testing.allocator;
     const io = std.testing.io;