app: e2e-tests: externalBackendToken: Retry removing temp profile

The "does not send the internal backend token to an unrelated port
owner" test keeps failing on the Windows arm64 runner, on every retry,
with EBUSY while deleting its temporary user data directory.

On Windows the test spawns Electron through a shell, so the pid it
kills and waits on is cmd.exe. That exits as soon as taskkill runs,
but Electron's child processes can hold files in the profile (the
DIPS database) open for a little longer, and rmSync hits them.

Let rmSync retry for up to about two seconds. Node only retries on
errors like EBUSY and EPERM, so a real failure still surfaces.

Signed-off-by: satyam kumar <krsatyamthakur@gmail.com>