[devdocsgjs/main: 1658/1867] Update Dart documentation (2.13.0)

[Andy Holmes <andyholmes src gnome org>]

commit 314010b205fa5aaaa91cfb9803f6a62306605622
Author: Simon Legner <Simon Legner gmail com>
Date:   Thu May 13 12:50:13 2021 +0200

    Update Dart documentation (2.13.0)

 lib/docs/filters/dart/clean_html.rb | 3 +++
 lib/docs/scrapers/dart.rb           | 2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)
---
diff --git a/lib/docs/filters/dart/clean_html.rb b/lib/docs/filters/dart/clean_html.rb
index f27bf093..4b8ee280 100644
--- a/lib/docs/filters/dart/clean_html.rb
+++ b/lib/docs/filters/dart/clean_html.rb
@@ -36,6 +36,9 @@ module Docs
         # Remove external links
         css('#external-links').remove
 
+        # Remove button to https://dart.dev/null-safety
+        css('.feature-null-safety').remove
+
         # Properly format header in v2 docs
         nested_title = at_css('div > h1')
         unless nested_title.nil?
diff --git a/lib/docs/scrapers/dart.rb b/lib/docs/scrapers/dart.rb
index c62a79e7..a7b92d9d 100644
--- a/lib/docs/scrapers/dart.rb
+++ b/lib/docs/scrapers/dart.rb
@@ -21,7 +21,7 @@ module Docs
     HTML
 
     version '2' do
-      self.release = '2.12.2'
+      self.release = '2.13.0'
       self.base_url = "https://api.dart.dev/stable/#{release}/";
     end