Async option removal was delayed til 6.0 (#7422)

* getsentry/sentry-ruby#1522

src/platforms/ruby/common/migration.mdx

@@ -133,7 +133,7 @@ config.timeout #=> config.transport.timeout
 config.open_timeout #=> config.transport.open_timeout
 config.proxy #=> config.transport.proxy
 
-# These options are present in sentry-ruby 4.* but has been removed in 5.0 with the faraday removal
+# These options are present in sentry-ruby 4.* but were removed in 5.0 with the faraday removal
 config.http_adapter #=> config.transport.http_adapter
 config.faraday_builder #=> config.transport.faraday_builder
 ```
@@ -281,7 +281,7 @@ config.before_send = lambda do |event, hint|
   if exception = hint[:exception]
     exception.raven_context.each do |key, value|
       # here I assume the event would be a Sentry::Event object
-      # it'll be a hash if you use the async callback though (which will be removed in version 5.0)
+      # however, it'll be a hash if you use the async callback (which will be removed in version 6.0)
       event.send("#{key}=", value)
     end
   end