Remove obsolete settings and code

[bramley]

Description

Remove some settings that are no longer used

USEFCK
USE_PDF
PHPMAILER
USE_EDITMESSAGE
USE_OUTLOOK_OPTIMIZED_HTML
WARN_SAVECHANGES
STACKED_ATTRIBUTE_SELECTION
USETINYMCEMESG
USETINYMCETEMPL
TINYMCEPATH
USE_SPAM_BLOCK
INTERFACELIB

Related Issue

Screenshots (if appropriate):

[michield]

USE_SPAMBLOCK is still in use: https://github.com/phpList/phplist3/blob/main/public_html/lists/index.php#L693

[michield]

Ah, but you mention that one in the description, but it's not removed from the code, so all good.

[bramley]

Ah, but you mention that one in the description, but it's not removed from the code, so all good.

Yes, I realised it was still in use so did put the code back, forgot to change the list in the description.

[phpListDockerBot]

This pull request has been mentioned on phpList Discuss. There might be relevant details there:

https://discuss.phplist.org/t/3-6-14-release-candidate-ready-for-testing/9109/1

[phpListDockerBot]

This pull request has been mentioned on phpList Discuss. There might be relevant details there:

https://discuss.phplist.org/t/phplist-3-6-14-released-security-release/9158/1