remove "blacklist" and "whitelist" (#4072)

.pylintrc

 [MASTER]
-# Add files or directories to the blacklist. They should be base names, not
+# Add files or directories to the ignore list. They should be base names, not
 # paths.
 ignore=CVS
 

markdown-link-check.full.json

         },
         {
             "pattern": "https://github.com/Unity-Technologies/ml-agents/(tree|archive)/release_[0-9]+.*",
-            "comment": "Whitelist future release tags"
+            "comment": "Allow future release tags"
         }
     ]
 }

utils/validate_meta_files.py

     asset_paths = ["Project/Assets", "com.unity.ml-agents"]
     meta_suffix = ".meta"
     python_suffix = ".py"
-    whitelist = frozenset(
+    allow_list = frozenset(
         [
             "com.unity.ml-agents/.editorconfig",
             "com.unity.ml-agents/.gitignore",
                     continue
 
                 full_path = os.path.join(root, f)
-                if full_path in whitelist:
+                if full_path in allow_list:
                     continue
 
                 # We expect each non-.meta file to have a .meta file, and each .meta file to have a non-.meta file