test: remove flaky designation for test_threadsafe_function

The test_threadsafe_function doesn't seem to be flaky anymore on
Windows. Optimistically removing the flaky designation in the relevant
status file.

Refs: nodejs#23621 (comment)

PR-URL: nodejs#26403
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

test/node-api/node-api.status

@@ -7,5 +7,3 @@ prefix node-api
 [true] # This section applies to all platforms
 
 [$system==win32]
-# https://github.com/nodejs/node/issues/23621
-test_threadsafe_function/test: PASS,FLAKY