test: aix: mark test_threadsafe_function/test flaky on AIX

Signed-off-by: Stewart X Addison <sxa@ibm.com>
PR-URL: nodejs#61452
Refs: nodejs#61441
Reviewed-By: Richard Lau <richard.lau@ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

Author: sxa

test/node-api/node-api.status

@@ -24,3 +24,7 @@ test_sea_addon/test: SKIP
 [$system==macos && $arch==x64]
 # https://github.com/nodejs/node/issues/59553
 test_sea_addon/test: SKIP
+
+[$system==aix]
+# https://github.com/nodejs/node/issues/61439
+test_threadsafe_function/test: PASS, FLAKY