SwiftLint: fixed lint with new 0.51.0 version (#2395)

See https://github.com/realm/SwiftLint/releases/tag/0.51.0

This new rule warns when rules are disabled without being enabled before
the end of the file.
We take advantage of that in many places, so it's better to disable it
here.

Author: NachoSoto

.swiftlint.yml

@@ -18,6 +18,7 @@ opt_in_rules:
 
 disabled_rules:
   - orphaned_doc_comment
+  - blanket_disable_command
 
 custom_rules:
   xctestcase_superclass: