make whitespace removal explicit

Co-authored-by: Gustave Granroth <gus.gran@gmail.com>

libraries/xcversion.rb

@@ -53,7 +53,7 @@ module MacOS
       def available_versions
         lines = shell_out!(XCVersion.list_available_xcodes).stdout.lines
         lines.reject { |line| line.start_with?(/\D/) }
-        lines.map { |line| line.chomp(' (installed)') }
+        lines.map { |line| line.chomp('(installed)').strip }
       end
     end
   end