increase maximum description lenght in UI

In the UI input, the number of glyphs is currently limited to
480 (with 8k max bytes). For larger groups with guidelines, more space
is needed.
This patch increases the number of glyphs and bytes by
a factor of eight to 3840 and 65536.
Signal community feature request: https://community.signalusers.org/t/expand-the-group-chat-description-or-pin-posts/65179

Author: isopod-a

SignalServiceKit/Groups/GroupManager.swift

@@ -31,8 +31,8 @@ public class GroupManager: NSObject {
     public static let maxGroupNameEncryptedByteCount: Int = 1024
     public static let maxGroupNameGlyphCount: Int = 32
 
-    public static let maxGroupDescriptionEncryptedByteCount: Int = 8192
-    public static let maxGroupDescriptionGlyphCount: Int = 480
+    public static let maxGroupDescriptionEncryptedByteCount: Int = 65536
+    public static let maxGroupDescriptionGlyphCount: Int = 3840
 
     // Epoch 1: Group Links
     // Epoch 2: Group Description