Bug 1568717 - update expectations redirect-https-downgrade.tentative.sub.html because of frequent passes. r=jgraham

Differential Revision: https://phabricator.services.mozilla.com/D54344

--HG--
extra : moz-landing-system : lando

testing/web-platform/meta/fetch/metadata/redirect/redirect-https-downgrade.tentative.sub.html.ini

@@ -14,9 +14,9 @@
       if (os == "linux") and not debug and not webrender and fission: FAIL
       if (os == "win") and debug and (processor == "x86") and fission: FAIL
       if (os == "linux") and not debug and webrender: FAIL
-      if os == "mac": FAIL
+      if os == "mac": ["TIMEOUT", "FAIL"]
       if os == "android": FAIL
-      [FAIL, TIMEOUT]
+      [FAIL, PASS, TIMEOUT]
 
   [Https downgrade track]
     expected: NOTRUN