Collapse duplicate pages related to updating old code

[drbyte]

Most of what's in /user/troubleshooting/php_debug_logs.md
is already in the more detailed /user/upgrading/php_warnings.md

(I just added a bunch of content to the latter, and then discovered the former had mostly duplicate content.)

Perhaps the former can be converted to a link to the latter? (I suspect a bunch of internal crosslinks may also require updating if we do that.)

Thoughts?

[scottcwilson]

OK

[scottcwilson]

I removed the duplicate content but kept the first page as a "why" - the second page is "how to fix." Take a look and see if you agree.