Revert disabling the spell check feature in defaults

This is not a change that should be done in a patch release.

CHANGELOG

@@ -3,7 +3,6 @@ CHANGELOG Roundcube Webmail
 
 RELEASE 1.4.12
 --------------
-- Disable the default spellchecker option using spell.roundcube.net (#8182)
 - Enigma: Fix bug where signature verification could fail for non-ascii bodies (#7919)
 - Fix bug where contacts search didn't work with addressbook_search_mods set to an empty array (#7974)
 - Fix bug causing some HTML message content to be not centered in Elastic skin (#7911)

config/defaults.inc.php

@@ -785,7 +785,7 @@ $config['show_real_foldernames'] = false;
 $config['quota_zero_as_unlimited'] = false;
 
 // Make use of the built-in spell checker.
-$config['enable_spellcheck'] = false;
+$config['enable_spellcheck'] = true;
 
 // Enables spellchecker exceptions dictionary.
 // Setting it to 'shared' will make the dictionary shared by all users.