Add 'forgiving_optional to win10 and plznav fyi bots

scripts/slave/gatekeeper.json

 {
   "comment": ["This is a configuration file for gatekeeper_ng.py",
               "Look at that for documentation on this file's format."],
 
   "masters": {
     "https://build.chromium.org/p/chromium": [
       {
         "categories": [
           "chromium_tree_closer"
         ],
@@ skipping 703 matching lines @@
         ]
       }
     ],
     "https://build.chromium.org/p/chromium.fyi": [
       {
         "builders": {
           "Browser Side Navigation Linux": {
             "tree_notify": [
               "plznavigate@chromium.org"
             ],
-            "forgive_all": "true"
+            "forgive_all": "true",
+            "forgiving_optional": ["*"]
           },
           "Closure Compilation Linux": {
             "tree_notify": [
               "dbeam+closure-bots@chromium.org",
               "fukino+closure-bots@chromium.org",
               "hirono+closure-bots@chromium.org",
               "vitalyp@chromium.org"
             ],
             "forgiving_steps": [
               "update_scripts",
@@ skipping 84 matching lines @@
             "tree_notify": [
               "krasin@chromium.org"
             ],
             "forgive_all": "true",
             "subject_template": "buildbot %(result)s in %(project_name)s on %(builder_name)s, revision %(revision)s"
           },
           "Win 10 Fast Ring": {
             "tree_notify": [
               "wfh@chromium.org"
             ],
-            "forgive_all": "true"
+            "forgive_all": "true",
+            "forgiving_optional": ["*"]
           }
         }
       }
     ]
   },
 
   "categories": {
     "chromium_memory_full": {
       "closing_optional": [
         "*"
@@ skipping 155 matching lines @@
         "cleanup_temp",
         "taskkill"
       ],
       "closing_optional": [
         "compile",
         "gn"
       ]
     }
   }
 }