Update base64 requirement from >= 0.1, < 0.3 to >= 0.1, < 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@v0.1.0...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.gemspec

@@ -20,7 +20,7 @@ Gem::Specification.new do |spec|
   spec.require_paths = ["lib"]
   spec.summary = "OpenVox, a community implementation of Puppet -- an automated configuration management tool"
   spec.specification_version = 4
-  spec.add_runtime_dependency('base64', '>= 0.1', '< 0.3')
+  spec.add_runtime_dependency('base64', '>= 0.1', '< 0.4')
   spec.add_runtime_dependency('benchmark', '>= 0.3', '< 0.5')
   spec.add_runtime_dependency('concurrent-ruby', '~> 1.0')
   spec.add_runtime_dependency('deep_merge', '~> 1.0')