Remove hardcoded version of rake from Bundler tests

The original commit is 85f73e42a5

spec/bundler/support/builders.rb

@@ -22,10 +22,6 @@ module Spec
       Gem::Platform.new(platform)
     end
 
-    def rake_version
-      "13.2.1"
-    end
-
     def build_repo1
       build_repo gem_repo1 do
         FileUtils.cp rake_path, "#{gem_repo1}/gems/"

spec/bundler/support/path.rb

@@ -280,6 +280,10 @@ module Spec
       Dir["#{base_system_gems}/#{Bundler.ruby_scope}/**/rake*.gem"].first
     end
 
+    def rake_version
+      File.basename(rake_path).delete_prefix("rake-").delete_suffix(".gem")
+    end
+
     private
 
     def git_ls_files(glob)