Update dependency to allow bigdecimal smaller than 4.x

Author: 0llirocks

cvss_suite.gemspec

@@ -37,7 +37,7 @@ in version 4.0, 3.1, 3.0 and 2.'
   spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
   spec.require_paths = ['lib']
 
-  spec.add_dependency "bigdecimal", ">= 3.1.8"
+  spec.add_dependency 'bigdecimal', '~> 3.1'
 
   spec.add_development_dependency 'bundler', '2.4.22'
   spec.add_development_dependency 'csv', '~> 3.3'