[bundler/bundler] Remove unneeded `to_s` calls

They are implicit inside `gem_command!`.

https://github.com/bundler/bundler/commit/6bdb13c899

spec/bundler/quality_spec.rb

@@ -231,7 +231,7 @@ RSpec.describe "The library itself" do
           spec = Gem::Specification.load(gemspec.to_s)
           spec.bindir = "libexec"
           File.open(root.join("bundler.gemspec").to_s, "w") {|f| f.write spec.to_ruby }
-          gem_command! :build, root.join("bundler.gemspec").to_s
+          gem_command! :build, root.join("bundler.gemspec")
           FileUtils.rm(root.join("bundler.gemspec").to_s)
         else
           gem_command! :build, gemspec

spec/bundler/support/helpers.rb

@@ -302,10 +302,10 @@ module Spec
             spec = Gem::Specification.load(gemspec.to_s)
             spec.bindir = "libexec"
             File.open(root.join("bundler.gemspec").to_s, "w") {|f| f.write spec.to_ruby }
-            Dir.chdir(root) { gem_command! :build, root.join("bundler.gemspec").to_s }
+            Dir.chdir(root) { gem_command! :build, root.join("bundler.gemspec") }
             FileUtils.rm(root.join("bundler.gemspec"))
           else
-            Dir.chdir(root) { gem_command! :build, gemspec.to_s }
+            Dir.chdir(root) { gem_command! :build, gemspec }
           end
           bundler_path = root.join("bundler-#{Bundler::VERSION}.gem")
         elsif g.to_s =~ %r{\A(?:[A-Z]:)?/.*\.gem\z}