Clear cell output doesn't always work

1. Create a cell with this code (this code is from one of our native notebooks tests)

print("Start")
import time
for i in range(100):
    time.sleep(0.1)
    print(i)

print("End")

1. Execute it
2. While it’s running and appending to output, execute ‘Clear All Cells Outputs’ a bunch of times
3. Eventually the cell will stop updating with output while continuing to run
4. Rerunning the cell will get it into a state where it never completes

[roblourens]

Fixed in https://github.com/microsoft/vscode/issues/121687

[joyceerhl]

Validated. Tried the original repro 5 times and everything works as expected. Thank you @roblourens!