Fix Lorekeeper::BacktraceCleaner to support BacktraceLocation

[ykitamura-mdsol]

observing the following error with Ruby3.2 + Rails7.1.2:

undefined method start_with?' for "../ruby/3.2.2/lib/ruby/gems/3.2.0/gems/actionpack-7.1.2/lib/action_dispatch/middleware/debug_exceptions.rb:34:in call'":Thread::Backtrace::Location`

This change was made in Rails (I guess from 7.1.0?):

• Use error_highlight gem to locate the columns where an error was raised rails/rails#45818

The result of the backtrace method can be an array of strings or an array of backtrace locations

Adding .to_s like in the PR