[CI] Ensure branches are String in bumpmatrix automation

Author: picandocodigo

rake_tasks/automation.rake

@@ -114,14 +114,14 @@ namespace :automation do
       if file == '.buildkite/pipeline.yml'
         require 'yaml'
         yaml = YAML.safe_load(content)
-        yaml_tests_branch = yaml['steps'][0]['env']['ES_YAML_TESTS_BRANCH']
+        yaml_tests_branch = yaml['steps'][0]['env']['ES_YAML_TESTS_BRANCH'].to_s
 
         if yaml_tests_branch == 'main'
           old = content.match(/STACK_VERSION: (.*)/)[1]
           new = "STACK_VERSION: #{version}"
           content.gsub!(new, old)
         else
-          branch = version.match(/([0-9]+\.[0-9]+)\.[0-9]+.*/)[1]
+          branch = version.to_s.match(/([0-9]+\.[0-9]+)\.[0-9]+.*/)[1]
           content.gsub!(yaml_tests_branch, branch)
         end
         puts "[#{yaml_tests_branch}] -> [#{branch}] in #{file.gsub('./', '')}"