Fix typo (SEPCIAL -> SPECIAL) (#6001)

install/tpl/debian6_dovecot2.conf.master

@@ -111,7 +111,7 @@ plugin {
   quota_status_overquota = "552 5.2.2 Mailbox is full"
 }
 
-imap_capability=+SEPCIAL-USE XLIST
+imap_capability=+SPECIAL-USE XLIST
 namespace inbox {
   inbox = yes
   separator = .

install/tpl/fedora_dovecot2.conf.master

@@ -105,7 +105,7 @@ plugin {
   quota_status_overquota = "552 5.2.2 Mailbox is full"
 }
 
-imap_capability=+SEPCIAL-USE XLIST
+imap_capability=+SPECIAL-USE XLIST
 namespace inbox {
   inbox = yes
   separator = .

install/tpl/opensuse_dovecot2.conf.master

@@ -104,7 +104,7 @@ plugin {
   quota_status_overquota = "552 5.2.2 Mailbox is full"
 }
 
-imap_capability=+SEPCIAL-USE XLIST
+imap_capability=+SPECIAL-USE XLIST
 namespace inbox {
   inbox = yes
   separator = .