Stop pinning a low ipywidgets version (#1455)

Summary:
#1273 set a maximum ipywidgets version since the then-most-recent version of Plotly wasn't compatible with the most current version. This is no longer necessary as of Plotly >=5.12.0.

Pull Request resolved: #1455

Test Plan:
Built the environment locally and ran code in a notebook that would have produced an error with incompatible plotly and ipywidgets versions, following [this issue](plotly/plotly.py#3686):

```python
import plotly.graph_objects as go

go.FigureWidget(go.Scatter(x=[1, 2, 3], y=[1, 4, 9]))
```

Reviewed By: mpolson64

Differential Revision: D43580470

Pulled By: esantorella

fbshipit-source-id: 644e8961a71c13758077ba590c07729a3c860010

Author: esantorella

setup.py

@@ -25,10 +25,9 @@
     "pandas",
     "scipy",
     "scikit-learn",
-    # ipywidgets 8.0.0 is incompatible with Plotly >=5.7.0
-    # https://github.com/plotly/plotly.py/issues/3686
-    "ipywidgets<8.0.0",
-    "plotly",
+    "ipywidgets",
+    # Needed for compatibility with ipywidgets >= 8.0.0
+    "plotly>=5.12.0",
     "typeguard",
 ]