(BOLT-1585) Fix bug for Psych support

The intended logic for deterining the correct invocation of the Psych method was flawed such that the "legacy" function invocation was always used. When the new Psych version shipped with ruby 3, the positional parameter is no longer supported. This commit updates the logic to correctly determine if the named argument is available in the Psych class.

Author: donoghuc

lib/bolt/pal/yaml_plan/loader.rb

@@ -50,7 +50,7 @@ def deserialize(node)
         def self.parse_plan(yaml_string, source_ref)
           # This passes the filename as the second arg for compatibility with Psych used with ruby < 2.6
           # This can be removed when we remove support for ruby 2.5
-          parse_tree = if Psych.method(:parse).parameters.include?('legacy_filename')
+          parse_tree = if Psych.method(:parse).parameters.rassoc(:filename)
                          Psych.parse(yaml_string, filename: source_ref)
                        else
                          Psych.parse(yaml_string, source_ref)