Bump proforma from v0.4 to v0.5

Bumps [proforma](https://github.com/openHPI/proforma) from v0.4 to v0.5.
- [Release notes](https://github.com/openHPI/proforma/releases)
- [Commits](b09c9fcc1f...b9e8769e79)

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

Gemfile

@@ -33,7 +33,7 @@ gem 'webpacker'
 gem 'rest-client'
 gem 'rubyzip'
 gem 'faraday'
-gem 'proforma', git: 'https://github.com/openHPI/proforma.git', tag: 'v0.4'
+gem 'proforma', git: 'https://github.com/openHPI/proforma.git', tag: 'v0.5'
 gem 'whenever', require: false
 gem 'rails-timeago'