do not add muted accounts to global counter

see discussion at
deltachat/deltachat-android#3143 (review) ,
there was the idea to show them as 'muted',
however, we tried the simple solution first, which make sense as well
and does not have the issue with the global counter on the badge icon
(where we could not use different colors)

deltachat-ios/DC/DcAccount.swift

@@ -120,7 +120,10 @@ public class DcAccounts {
         let skipId = skipCurrent ? getSelected().id : -1
         for accountId in getAll() {
             if accountId != skipId {
-                freshCount += get(id: accountId).getFreshMessages().count
+                let dcContext = get(id: accountId)
+                if !dcContext.isMuted() {
+                    freshCount += dcContext.getFreshMessages().count
+                }
             }
         }
         return freshCount