Update 'contributors' to 'interpretation' in Visualize Results for Multivariate API Demo Notebook.ipynb

> Please provide us with the following information:
> ---------------------------------------------------------------

### This issue is for a: (mark with an `x`)
```
- [ x] bug report -> please search issues before submitting
- [ ] feature request
- [ ] documentation issue or request
- [ ] regression (a behavior that used to work and stopped in a new release)
```

### Minimal steps to reproduce
> Run the Multivariate API Demo Notebook.ipynb notebook

### Any log messages given by the failure
>Traceback (most recent call last):
File "anomaly_detector/visualize.py", line 183, in
show_contribution(series, raw_result, top_anomaly)
File "anomaly_detector/visualize.py", line 148, in show_contribution
anomaly_result = [
IndexError: list index out of range

### Expected/desired behavior
> Display plots

### OS and Version?
> Windows 10 / WSL 2.0

### Versions
>

### Mention any other details that might be useful
Current example:

def show_contribution(series, raw_result, anomaly_timestamp):
anomaly_result = [x for x in raw_result['results'] if 'contributors' in x['value'] and x['timestamp'] == top_anomaly][0]
contributors = [x['variable'] for x in anomaly_result['value']['contributors']]

Fixed example:
def show_contribution(series, raw_result, anomaly_timestamp):
anomaly_result = [x for x in raw_result['results'] if 'interpretation' in x['value'] and x['timestamp'] == top_anomaly][0]
contributors = [x['variable'] for x in anomaly_result['value']['interpretation']]
> ---------------------------------------------------------------
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