[rubygems/rubygems] Simplify `lockfile_platforms` helper

To make it easier to change the default platforms that get locked later.

https://github.com/rubygems/rubygems/commit/255c4012ec

spec/bundler/bundler/definition_spec.rb

@@ -154,7 +154,7 @@ RSpec.describe Bundler::Definition do
             only_java (1.1-java)
 
         PLATFORMS
-          #{lockfile_platforms_for("java", specific_local_platform)}
+          #{lockfile_platforms("java")}
 
         DEPENDENCIES
           only_java

spec/bundler/install/gemfile/gemspec_spec.rb

@@ -674,7 +674,7 @@ RSpec.describe "bundle install from an existing gemspec" do
             railties (6.1.4)
 
         PLATFORMS
-          #{lockfile_platforms_for("java", specific_local_platform)}
+          #{lockfile_platforms("java")}
 
         DEPENDENCIES
           activeadmin!

spec/bundler/install/gemfile/specific_platform_spec.rb

@@ -514,7 +514,7 @@ RSpec.describe "bundle install with specific platforms" do
             sorbet-runtime (= 0.5.10160)
 
       PLATFORMS
-        #{lockfile_platforms_for([specific_local_platform, "ruby"])}
+        #{lockfile_platforms("ruby")}
 
       DEPENDENCIES
         sorbet-static-and-runtime
@@ -769,7 +769,7 @@ RSpec.describe "bundle install with specific platforms" do
           nokogiri (1.13.8-#{Gem::Platform.local})
 
       PLATFORMS
-        #{lockfile_platforms_for([specific_local_platform, "ruby"])}
+        #{lockfile_platforms("ruby")}
 
       DEPENDENCIES
         nokogiri

spec/bundler/lock/lockfile_spec.rb

@@ -982,7 +982,7 @@ RSpec.describe "the lockfile format" do
           rack (1.0.0)
 
       PLATFORMS
-        #{lockfile_platforms_for("java", specific_local_platform)}
+        #{lockfile_platforms("java")}
 
       DEPENDENCIES
         rack

spec/bundler/runtime/platform_spec.rb

@@ -86,7 +86,7 @@ RSpec.describe "Bundler.setup with multi platform stuff" do
           racc (1.5.2)
 
       PLATFORMS
-        #{lockfile_platforms_for("ruby", specific_local_platform)}
+        #{lockfile_platforms("ruby")}
 
       DEPENDENCIES
         nokogiri (~> 1.11)

spec/bundler/support/platforms.rb

@@ -99,12 +99,8 @@ module Spec
       9999
     end
 
-    def lockfile_platforms
-      lockfile_platforms_for(specific_local_platform)
-    end
-
-    def lockfile_platforms_for(*platforms)
-      platforms.map(&:to_s).sort.join("\n  ")
+    def lockfile_platforms(*extra)
+      [specific_local_platform, *extra].map(&:to_s).sort.join("\n  ")
     end
   end
 end