Update rake requirement from 13.0.3 to 13.0.6

Updates the requirements on [rake](https://github.com/ruby/rake) to permit the latest version.
- [Release notes](https://github.com/ruby/rake/releases)
- [Changelog](https://github.com/ruby/rake/blob/master/History.rdoc)
- [Commits](ruby/rake@v13.0.3...v13.0.6)

---
updated-dependencies:
- dependency-name: rake
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Gemfile

@@ -1,6 +1,6 @@
 source 'https://rubygems.org'
 
-gem 'rake', '13.0.3'
+gem 'rake', '13.0.6'
 gem 'asciidoctor', '2.0.15'
 
 gem 'json', '2.5.1'