Merge pull request rails#50683 from p8/activerecord/configurations-docs-typo

Fix typo in ActiveRecord::Core.configurations doc [ci-skip]

Author: fatkodima

activerecord/lib/active_record/core.rb

@@ -73,7 +73,7 @@ def self.configurations=(config)
       end
       self.configurations = {}
 
-      # Returns fully resolved ActiveRecord::DatabaseConfigurations object
+      # Returns a fully resolved ActiveRecord::DatabaseConfigurations object.
       def self.configurations
         @@configurations
       end