Deprecated code removal

[colemanw]

Overview

Removes code that's been noisily deprecated > 3 years; ensures more recently noisy deprecations have an accompanying @deprecated annotation.

[civibot]

(Standard links)

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[totten]

Searched universe for several of these and agree they aren't used: pendingToConfirmSpaces(), _html2pdf_tcpdf(), and (fromCRM_Utils_System) urlEncode() and relativeURL().

I didn't check the bits in CRM/Event/Form/Participant.php.

[eileenmcnaughton]

I confirmed the 2 bits that were not listed above have been deprecated since early 2020 - I didn't double check the deprecation dates on the functions being removed since I think doing EITHER a check on when the noisy deprecation was added OR a universe check is appropriate & the universe check is done per the comments above