Update base64 requirement from ~> 0.2.0 to >= 0.2, < 0.4

Updates the requirements on [base64](https://github.com/ruby/base64) to permit the latest version.
- [Release notes](https://github.com/ruby/base64/releases)
- [Commits](ruby/base64@v0.2.0...v0.3.0)

---
updated-dependencies:
- dependency-name: base64
  dependency-version: 0.3.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

puppet-blacksmith.gemspec

@@ -16,7 +16,7 @@ Gem::Specification.new do |s|
 
   s.required_ruby_version = '>= 2.7.0'
 
-  s.add_dependency 'base64', '~> 0.2.0'
+  s.add_dependency 'base64', '>= 0.2', '< 0.4'
   s.add_dependency 'puppet-modulebuilder', '~> 2.0', '>= 2.0.2'
   s.add_dependency 'rest-client', '~>2.0'
   s.add_development_dependency 'aruba', '~> 2.1'