refactor: do not use future-deprecated `DATE_RFC7231` constant #13466

Job	Run time
Setup PHP Version for Code Coverage	2s
Others (8.1) / Sanity Tests	2m 53s
Others (8.4) / Sanity Tests	2m 21s
Others (8.2) / Sanity Tests	4m 14s
Others (8.3) / Sanity Tests	2m 40s
SeparateProcess (8.2) / tests	3m 51s
SeparateProcess (8.4) / tests	3m 46s
DatabaseLive (8.2, SQLite3, 8.0) / tests	3m 22s
SeparateProcess (8.1) / tests	3m 36s
DatabaseLive (8.4, Postgre, 8.0) / tests	2m 45s
DatabaseLive (8.1, MySQLi, 5.7) / tests	3m 10s
DatabaseLive (8.1, SQLite3, 8.0) / tests	3m 14s
SeparateProcess (8.3) / tests	3m 47s
DatabaseLive (8.1, OCI8, 8.0) / tests	6m 37s
DatabaseLive (8.3, Postgre, 8.0) / tests	3m 5s
DatabaseLive (8.1, SQLSRV, 8.0) / tests	6m 4s
DatabaseLive (8.4, OCI8, 8.0) / tests	6m 19s
DatabaseLive (8.3, SQLite3, 8.0) / tests	3m 9s
DatabaseLive (8.4, SQLite3, 8.0) / tests	2m 57s
DatabaseLive (8.4, MySQLi, 8.0) / tests	5m 18s
DatabaseLive (8.1, Postgre, 8.0) / tests	2m 51s
DatabaseLive (8.2, MySQLi, 8.0) / tests	5m 15s
DatabaseLive (8.2, SQLSRV, 8.0) / tests	6m 11s
DatabaseLive (8.4, SQLSRV, 8.0) / tests	4m 37s
DatabaseLive (8.3, MySQLi, 8.0) / tests	5m 14s
DatabaseLive (8.3, OCI8, 8.0) / tests	6m 44s
DatabaseLive (8.1, MySQLi, 8.0) / tests	4m 16s
DatabaseLive (8.2, OCI8, 8.0) / tests	7m 22s
DatabaseLive (8.2, Postgre, 8.0) / tests	3m 21s
DatabaseLive (8.3, SQLSRV, 8.0) / tests	5m 18s
CacheLive (8.1) / Cache Live Tests	2m 3s
CacheLive (8.3) / Cache Live Tests	2m 18s
CacheLive (8.2) / Cache Live Tests	2m 19s
CacheLive (8.4) / Cache Live Tests	1m 58s
Upload coverage results to Coveralls / coveralls	46s
	2h 13m 43s

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