Avoid usage of for..in to be optimizable.

Before this patch:

```
[marking Qlobber._match 0x2387f8d59ba8 for recompilation, reason: hot and stable, ICs with typeinfo: 16/27 (59%)]
[disabled optimization for Qlobber._match, reason: ForInStatement is not fast case]
```

after

```
[optimizing: Qlobber._match / 27f4b2159c59 - took 0.149, 0.378, 0.000 ms]
```