test: mark test_threadsafe_function/test as flaky

The test fails consistently on windows-fanned with vs2017.
mark it as flaky while the issue is being progressed, and
to keep CI green / amber.

Ref: nodejs#23621
PR-URL: nodejs#24714
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

test/addons-napi/addons-napi.status

@@ -0,0 +1,11 @@
+prefix addons-napi
+
+# To mark a test as flaky, list the test name in the appropriate section
+# below, without ".js", followed by ": PASS,FLAKY". Example:
+# sample-test                        : PASS,FLAKY
+
+[true] # This section applies to all platforms
+
+[$system==win32]
+# https://github.com/nodejs/node/issues/23621
+test_threadsafe_function/test: PASS,FLAKY