Remove invalid assert in case of legitimately stacking unicode

This assert was being falsely triggered by legitimate unicode.

The current state of affairs (unchanged by this PR) is that all
diacriticals will be stripped from a message that also contains e.g. 3
flags in a sequence.

// FREEBIE

Signal/src/util/DisplayableTextFilter.swift

@@ -17,7 +17,6 @@ import Foundation
         if (self.hasExcessiveDiacriticals(text: text)) {
             Logger.warn("\(TAG) filtering text for excessive diacriticals.")
             let filteredText = text.folding(options: .diacriticInsensitive, locale: .current)
-            assert(!self.hasExcessiveDiacriticals(text: filteredText))
             return filteredText
         }