Bug Fix: Fix data table icons in dark mode (#6409)

## Motivation for features / changes
The sort icons should turn white in dark mode. This seems to be a bug
with material icons having set the fill attribute of the svg path to
black for the down arrow icon.

The up arrow (which works)

![image](https://github.com/tensorflow/tensorboard/assets/78179109/995455e3-84ae-482f-92be-df8a2b463ef0)

The down arrow (which does not)

![image](https://github.com/tensorflow/tensorboard/assets/78179109/a46201ff-dd15-440a-accc-1db71106d00c)

## Technical description of changes

## Screenshots of UI changes (or N/A)
Before

![image](https://github.com/tensorflow/tensorboard/assets/78179109/65c2eacd-26c8-43a4-aaef-68c5700cb675)

After:

![image](https://github.com/tensorflow/tensorboard/assets/78179109/6d1369f7-17c1-4f38-9603-8869233acfb5)


## Alternate designs / implementations considered (or N/A)
We are using the icon from version 3.0.1 but when I checked version
4.0.0 (the newest) the problem had not been fixed.

Author: rileyajones

tensorboard/webapp/widgets/data_table/data_table_component.scss

@@ -85,6 +85,10 @@ $_accent: map-get(mat.get-color-config($tb-theme), accent);
   .cell mat-icon {
     height: 12px;
     width: 12px;
+
+    ::ng-deep path {
+      fill: unset;
+    }
   }
 
   .sorting-icon-container {