Force Plots Display Bug

Per @freddyaboulton's second review on #2157 , we'd like to look into the bug that he found and determine what the root cause is and whether it's tied to the display() function or not.

Repro:

```
from evalml.demos import load_fraud
from evalml.pipelines import BinaryClassificationPipeline
from evalml.model_understanding import explain_predictions
from evalml.model_understanding.force_plots import graph_force_plot
import pytest

X, y = load_fraud(1000)

pipeline = BinaryClassificationPipeline(["Text Featurization Component", "DateTime Featurization Component",
"One Hot Encoder", "Random Forest Classifier"])
pipeline.fit(X, y)

results = graph_force_plot(pipeline, rows_to_explain=[1],
training_data=X, y=y)

for result in results:
for cls in result:
print("Class:", cls)
display(result[cls]["plot"])

```