CI: Mark release gem group as optional

Author: bastelfreak

.github/workflows/test.yml

@@ -6,9 +6,6 @@ on:
     branches:
       - master
 
-env:
-  BUNDLE_WITHOUT: release
-
 jobs:
   test:
     runs-on: ubuntu-latest

Gemfile

@@ -2,7 +2,7 @@ source 'https://rubygems.org'
 
 gemspec
 
-group :release do
-  gem 'faraday-retry', require: false
-  gem 'github_changelog_generator', require: false
+group :release, optional: true do
+  gem 'faraday-retry', '~> 2.1', require: false
+  gem 'github_changelog_generator', '~> 1.16.4', require: false
 end