Ignore missing JSON files with `FileNotFoundError` except

## `KeyError` -> `FileNotFoundError` in Handling Missing Files

In loading the dataset, the following error was raised:

```
FileNotFoundError: [Errno 2] No such file or directory: '~/.cache/huggingface/datasets/downloads/extracted/807f2a9200aa3db507d051a944437b7c8c5eb0de21039735c683affca111c338/WikiTables-WithLinks/tables_tok/The_Real_World:_Brooklyn_0.json'
```

As this error is due to the file `The_Real_World:_Brooklyn_0.json` missing from the repo, it should be caught in the comment made on line 147 ("...filenames with ':'").

However, the `except` clause needs to catch `FileNotFoundError` instead of `KeyError`.

Long-term, would be great to have the missing files handled in this dataset! But short-term, it seems like this PR will fix things (:

hybrid_qa.py

@@ -144,7 +144,7 @@ class HybridQa(datasets.GeneratorBasedBuilder):
                     table = json.load(f)
                 with open(url_data_path, encoding="utf-8") as f:
                     url_data = json.load(f)
-            except KeyError:  # Some JSON files were not properly added to the GitHub repo: filenames with ':', '"'
+            except FileNotFoundError:  # Some JSON files were not properly added to the GitHub repo: filenames with ':', '"'
                 continue
 
             table["header"] = [header[0] for header in table["header"]]