Remove support for EOL Ruby 2.5

.github/workflows/test.yml

@@ -13,7 +13,7 @@ jobs:
         orm: [active_record]
         adapter: [sqlite3]
         include:
-          - ruby: 2.5
+          - ruby: 2.6
             gemfile: gemfiles/rails_6.0.gemfile
             orm: active_record
             adapter: sqlite3

.rubocop.yml

@@ -8,7 +8,6 @@ AllCops:
     - "spec/dummy_app/tmp/**/*"
     - "vendor/bundle/**/*"
   NewCops: disable
-  TargetRubyVersion: 2.5
 
 Gemspec/DateAssignment:
   Enabled: true

README.md

@@ -98,7 +98,6 @@ If you think you found a bug in RailsAdmin, you can [submit an issue](https://gi
 
 This library aims to support and is [tested against][ghactions] the following Ruby implementations:
 
-- Ruby 2.5
 - Ruby 2.6
 - Ruby 2.7
 - Ruby 3.0

lib/rails_admin/bootstrap-sass/sass_functions.rb

@@ -8,7 +8,7 @@ def ie_hex_str(color)
         assert_type color, :Color
         alpha = (color.alpha * 255).round
         alphastr = alpha.to_s(16).rjust(2, '0')
-        Sass::Script::String.new("##{alphastr}#{color.send(:hex_str)[1..-1]}".upcase)
+        Sass::Script::String.new("##{alphastr}#{color.send(:hex_str)[1..]}".upcase)
       end
       declare :ie_hex_str, [:color] if respond_to?(:declare)
     end

rails_admin.gemspec

@@ -25,7 +25,7 @@ Gem::Specification.new do |spec|
   spec.homepage = 'https://github.com/railsadminteam/rails_admin'
   spec.name = 'rails_admin'
   spec.require_paths = %w[lib]
-  spec.required_ruby_version     = '>= 2.5.0'
+  spec.required_ruby_version     = '>= 2.6.0'
   spec.required_rubygems_version = '>= 1.8.11'
   spec.summary = 'Admin for Rails'
   spec.version = RailsAdmin::Version

spec/integration/actions/export_spec.rb

@@ -86,7 +86,7 @@
     click_button 'Export to csv'
     csv = CSV.parse page.driver.response.body
     expect(csv[0]).to match_array ['Id', 'Commentable', 'Commentable type', 'Content', 'Created at', 'Updated at']
-    csv[1..-1].each do |line|
+    csv[1..].each do |line|
       expect(line[csv[0].index('Commentable')]).to eq(@player.id.to_s)
       expect(line[csv[0].index('Commentable type')]).to eq(@player.class.to_s)
     end

spec/integration/actions/index_spec.rb

@@ -898,7 +898,7 @@ def visit_page(page)
           end
         end
       end
-      visit index_path(model_name: 'player', query: player.name[1..-1])
+      visit index_path(model_name: 'player', query: player.name[1..])
       is_expected.to have_no_content(player.name)
     end
   end
@@ -1141,7 +1141,7 @@ def visit_page(page)
       visit index_path(model_name: 'team')
       cols = all('th').collect(&:text)
       expect(cols[0..3]).to eq(all_team_columns[1..4])
-      expect(cols).to contain_exactly(*all_team_columns[1..-1])
+      expect(cols).to contain_exactly(*all_team_columns[1..])
       expect(page).to have_selector('.ra-sidescroll[data-ra-sidescroll=2]')
     end
 
@@ -1225,7 +1225,7 @@ def visit_page(page)
       visit index_path(model_name: 'team')
       cols = all('th').collect(&:text)
       expect(cols[0..3]).to eq(all_team_columns[1..4])
-      expect(cols).to contain_exactly(*all_team_columns[1..-1])
+      expect(cols).to contain_exactly(*all_team_columns[1..])
       expect(page).to have_selector('.ra-sidescroll[data-ra-sidescroll=3]')
     end
   end

spec/rails_admin/adapters/active_record_spec.rb

@@ -101,7 +101,7 @@ class PlayerWithDefaultScope < Player
 
     it '#destroy destroys multiple items' do
       abstract_model.destroy(@players[0..1])
-      expect(Player.all).to eq(@players[2..-1])
+      expect(Player.all).to eq(@players[2..])
     end
 
     it '#where returns filtered results' do