Bump sitemap_generator from 6.0.2 to 6.1.2

Bumps [sitemap_generator](https://github.com/kjvarga/sitemap_generator) from 6.0.2 to 6.1.2.
- [Release notes](https://github.com/kjvarga/sitemap_generator/releases)
- [Changelog](https://github.com/kjvarga/sitemap_generator/blob/master/CHANGES.md)
- [Commits](https://github.com/kjvarga/sitemap_generator/compare/v6.0.2...v6.1.2)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Gemfile.lock

@@ -545,7 +545,7 @@ GEM
       json (>= 1.8, < 3)
       simplecov-html (~> 0.10.0)
     simplecov-html (0.10.2)
-    sitemap_generator (6.0.2)
+    sitemap_generator (6.1.2)
       builder (~> 3.0)
     smart_properties (1.13.1)
     social-share-button (1.1.0)
@@ -711,7 +711,7 @@ DEPENDENCIES
   savon (~> 2.12.0)
   scss_lint (~> 0.59.0)
   selenium-webdriver (~> 3.142)
-  sitemap_generator (~> 6.0.2)
+  sitemap_generator (~> 6.1.2)
   social-share-button (~> 1.1)
   spring (~> 2.1.1)
   spring-commands-rspec (~> 1.0.4)