Releasing both pressed Shift keys (left+right) reports only one

### Windows Terminal version

current main

### Windows build number

10.0.19045.5011

### Other Software

_No response_

### Steps to reproduce

1. Activate "debug tap" pane.
- Add the global setting (near the top of your JSON file):
```
"debugFeatures": true
```
- Open a new tab while holding down both left and right Alt .
2. Press and release both Shift keys simultaneously.

### Expected Behavior

There are four reports in the "debug tap" pane:
- The first Shift key was pressed.
- The second Shift key was pressed.
- Some Shift key was released.
- The remaining Shift key was released.

### Actual Behavior


There are only three reports in the "debug tap" pane:
- The first Shift key was pressed.
- The second Shift key was pressed.
- Some Shift key was released.

Reproduce this in Windows Terminal by enabling the debug tap pane with the global "debugFeatures": true setting, opening a tab while holding both Alt keys, and pressing and releasing both Shift keys. Compare the debug tap reports for the two press and two release events; done means both Shift releases are reported separately, matching the expected four reports.

Written by the indexing model from the issue text.