refactor: remove deprecated `BaseHandler::RESERVED_CHARACTERS` constant #14407

Job	Run time
Setup PHP Version for Code Coverage	4s
Others (8.2) / Sanity Tests	4m 42s
Others (8.5) / Sanity Tests	2m 44s
Others (8.4) / Sanity Tests	2m 45s
Others (8.3) / Sanity Tests	2m 35s
CacheLive (8.5) / Cache Live Tests	2m 10s
CacheLive (8.3) / Cache Live Tests	2m 17s
CacheLive (8.4) / Cache Live Tests	2m 17s
SeparateProcess (8.4) / tests	3m 47s
SeparateProcess (8.5) / tests	3m 9s
DatabaseLive (8.5, Postgre, 8.0) / tests	2m 57s
CacheLive (8.2) / Cache Live Tests	2m 37s
DatabaseLive (8.3, Postgre, 8.0) / tests	2m 58s
SeparateProcess (8.2) / tests	3m 14s
DatabaseLive (8.5, SQLite3, 8.0) / tests	2m 31s
DatabaseLive (8.2, Postgre, 8.0) / tests	3m 56s
DatabaseLive (8.4, SQLSRV, 8.0) / tests	5m 35s
DatabaseLive (8.4, OCI8, 8.0) / tests	6m 58s
DatabaseLive (8.3, OCI8, 8.0) / tests	7m 41s
DatabaseLive (8.4, SQLite3, 8.0) / tests	2m 22s
SeparateProcess (8.3) / tests	3m 51s
DatabaseLive (8.5, MySQLi, 8.0) / tests	5m 14s
DatabaseLive (8.2, MySQLi, 5.7) / tests	4m 16s
DatabaseLive (8.2, SQLSRV, 8.0) / tests	5m 52s
DatabaseLive (8.2, SQLite3, 8.0) / tests	2m 53s
DatabaseLive (8.3, SQLite3, 8.0) / tests	2m 35s
DatabaseLive (8.5, OCI8, 8.0) / tests	6m 41s
DatabaseLive (8.4, Postgre, 8.0) / tests	2m 52s
DatabaseLive (8.5, SQLSRV, 8.0) / tests	5m 53s
DatabaseLive (8.3, SQLSRV, 8.0) / tests	5m 37s
DatabaseLive (8.2, MySQLi, 8.0) / tests	6m 35s
DatabaseLive (8.4, MySQLi, 8.0) / tests	5m 14s
DatabaseLive (8.3, MySQLi, 8.0) / tests	5m 45s
DatabaseLive (8.2, OCI8, 8.0) / tests	8m 25s
Upload coverage results to Coveralls / coveralls	44s
	2h 19m 46s

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