Feature: #4870-Roundcube Update auf RC 1.6.6

Description

Fix regression in handling LDAP search_fields configuration parameter (#9210)
Enigma: Fix finding of a private key when decrypting a message using GnuPG v2.3
Fix page jump menu flickering on click (#9196)
Update to TinyMCE 5.10.9 security release (#9228)
Fix PHP8 warnings (#9235, #9238, #9242, #9306)
Fix saving other encryption settings besides enigma's (#9240)
Fix unneeded php command use in installto.sh and deluser.sh scripts (#9237)
Fix TinyMCE localization installation (#9266)
Fix bug where trailing non-ascii characters in email addresses could have been removed in recipient input (#9257)
Fix IMAP GETMETADATA command with options - RFC5464