Revert "Move irb detection to top-level before(:each) block"

This reverts commit 261f8023842b6f90007df68dfc3d88a01a9337a2.

spec/bundler/commands/platform_spec.rb

@@ -941,12 +941,6 @@ G
 
   context "bundle console", bundler: "< 3" do
     before do
-      begin
-        require "irb"
-      rescue LoadError
-        skip "This spec requires IRB to be available"
-      end
-
       install_gemfile <<-G
         source "https://gem.repo1"
         gem "myrack"
@@ -956,6 +950,12 @@ G
     end
 
     it "starts IRB with the default group loaded when ruby version matches", :readline do
+      begin
+        require "irb"
+      rescue LoadError
+        skip "This spec requires IRB to be available"
+      end
+
       gemfile <<-G
         source "https://gem.repo1"
         gem "myrack"