Update ruby version to 2.4.5

* delete ruby 2.3.7 version in Gemfile
* delete .ruby-version for local file with development

Gemfile

@@ -1,8 +1,6 @@
 source 'https://gems.ruby-china.com'
 git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 
-ruby '2.3.7'
-
 gem 'rails', '~> 5.2.0'
 gem 'mysql2', '>= 0.4.4', '< 0.6.0'
 gem 'puma', '~> 3.11'

Gemfile.lock

@@ -490,8 +490,5 @@ DEPENDENCIES
   web-console (>= 3.3.0)
   wkhtmltopdf-binary
 
-RUBY VERSION
-   ruby 2.3.7p456
-
 BUNDLED WITH
    2.1.4