hci-theme: bump version to 0.2.1, reduce dependencies

hci-theme.gemspec

@@ -3,7 +3,7 @@ require 'rake'
 
 Gem::Specification.new do |spec|
   spec.name          = "hci-theme"
-  spec.version       = "0.2.0"
+  spec.version       = "0.2.1"
   spec.authors       = ["Jan-Philipp Stauffert"]
   spec.email         = ["jan-philipp.stauffert@uni-wuerzburg.de"]
 
@@ -26,11 +26,10 @@ Gem::Specification.new do |spec|
     'assets/images/*'
   ].to_a
 
-  spec.required_ruby_version = '>= 2.4.0'
+  spec.required_ruby_version = '>= 2.7.0'
 
   spec.add_runtime_dependency "jekyll", "~> 4.0"
-  spec.add_runtime_dependency 'jekyll-sass-converter', "~> 2.0"
 
-  spec.add_development_dependency "bundler", "~> 2.1.4"
+  spec.add_development_dependency "bundler", "~> 2.1"
   spec.add_development_dependency "rake", "~> 12.0"
 end