[rubygems/rubygems] Remove "double CI" for testing Bundler 4 mode

Since now every functionality that changes in Bundler 4 is under a
setting, we can enable that setting to test the new functionality,
without having to run our full CI twice.

This can actually be seen as increasing coverage, because Bundler 4
functionality will now be tested on Windows, MacOS, or any other
environment where previously "Bundler 4 mode" was not running.

ruby/rubygems@1cb3e009fc

Author: deivid-rodriguez

lib/bundler/feature_flag.rb

@@ -50,8 +50,6 @@ def deprecated_major?(target_major_version)
       @major_version >= target_major_version
     end
 
-    attr_reader :bundler_version
-
     def initialize(bundler_version)
       @bundler_version = Gem::Version.create(bundler_version)
       @major_version = @bundler_version.segments.first

spec/bundler/bundler/cli_spec.rb

@@ -250,7 +250,7 @@ def out_with_macos_man_workaround
 end
 
 RSpec.describe "bundler executable" do
-  it "shows the bundler version just as the `bundle` executable does", bundler: "2" do
+  it "shows the bundler version just as the `bundle` executable does" do
     bundler "--version"
     expect(out).to eq("Bundler version #{Bundler::VERSION}")
   end

spec/bundler/bundler/current_ruby_spec.rb

@@ -139,13 +139,13 @@
   end
 
   describe "Deprecated platform" do
-    it "Outputs a deprecation warning when calling maglev?", bundler: "2" do
+    it "Outputs a deprecation warning when calling maglev?" do
       expect(Bundler.ui).to receive(:warn).with(/`CurrentRuby#maglev\?` is deprecated with no replacement./)
 
       Bundler.current_ruby.maglev?
     end
 
-    it "Outputs a deprecation warning when calling maglev_31?", bundler: "2" do
+    it "Outputs a deprecation warning when calling maglev_31?" do
       expect(Bundler.ui).to receive(:warn).with(/`CurrentRuby#maglev_31\?` is deprecated with no replacement./)
 
       Bundler.current_ruby.maglev_31?

spec/bundler/bundler/dsl_spec.rb

@@ -103,7 +103,7 @@
       )
     end
 
-    context "default hosts", bundler: "2" do
+    context "default hosts" do
       it "converts :github to URI using https" do
         subject.gem("sparks", github: "indirect/sparks")
         github_uri = "https://github.com/indirect/sparks.git"

spec/bundler/bundler/settings_spec.rb

@@ -333,7 +333,7 @@
       C
 
       expect(Bundler.ui).not_to receive(:warn)
-      expect(settings.all).to eq(simulated_version ? ["simulate_version"] : [])
+      expect(settings.all).to be_empty
     end
 
     it "converts older keys with dashes" do

spec/bundler/cache/path_spec.rb

@@ -97,7 +97,7 @@
     expect(bundled_app("vendor/cache/foo-1.0")).not_to exist
   end
 
-  it "does not cache path gems by default", bundler: "2" do
+  it "does not cache path gems by default" do
     build_lib "foo"
 
     install_gemfile <<-G

spec/bundler/commands/binstubs_spec.rb

@@ -168,7 +168,7 @@
       expect(bundled_app("exec/myrackup")).to exist
     end
 
-    it "setting is saved for bundle install", bundler: "2" do
+    it "setting is saved for bundle install" do
       install_gemfile <<-G
         source "https://gem.repo1"
         gem "myrack"

spec/bundler/commands/cache_spec.rb

@@ -158,7 +158,7 @@
     end
   end
 
-  context "with --path", bundler: "2" do
+  context "with --path" do
     it "sets root directory for gems" do
       gemfile <<-D
         source "https://gem.repo1"
@@ -221,7 +221,7 @@
       expect(bundled_app("vendor/cache/myrack-1.0.0.gem")).to exist
     end
 
-    it "puts the gems in vendor/cache even for legacy windows rubies, but prints a warning", bundler: "2" do
+    it "puts the gems in vendor/cache even for legacy windows rubies, but prints a warning" do
       gemfile <<-D
         source "https://gem.repo1"
         gem 'myrack', :platforms => [:ruby_20, :x64_mingw_20]

spec/bundler/commands/check_spec.rb

@@ -123,7 +123,7 @@
     expect(err).to include("Bundler can't satisfy your Gemfile's dependencies.")
   end
 
-  it "remembers --without option from install", bundler: "2" do
+  it "remembers --without option from install" do
     gemfile <<-G
       source "https://gem.repo1"
       group :foo do
@@ -272,7 +272,7 @@
     expect(last_command).to be_failure
   end
 
-  context "--path", bundler: "2" do
+  context "--path" do
     context "after installing gems in the proper directory" do
       before do
         gemfile <<-G

spec/bundler/commands/clean_spec.rb

@@ -383,7 +383,7 @@ def should_not_have_gems(*gems)
     expect(out).to include("myrack (1.0.0)").and include("thin (1.0)")
   end
 
-  it "--clean should override the bundle setting on install", bundler: "2" do
+  it "--clean should override the bundle setting on install" do
     gemfile <<-G
       source "https://gem.repo1"
 
@@ -405,7 +405,7 @@ def should_not_have_gems(*gems)
     should_not_have_gems "thin-1.0"
   end
 
-  it "--clean should override the bundle setting on update", bundler: "2" do
+  it "--clean should override the bundle setting on update" do
     build_repo2
 
     gemfile <<-G