Revert "ux: Mute selected text"

I had to revert this for now because it conflicts too heavily
with the highlighter feature which we definitely want in master.

Let's rework this using Daniel's refactor

This reverts commit d663155941.

damus/Views/Muting/AddMuteItemView.swift

@@ -8,7 +8,7 @@ import SwiftUI
 
 struct AddMuteItemView: View {
     let state: DamusState
-    @Binding var new_text: String
+    @State var new_text: String = ""
     @State var expiration: DamusDuration = .indefinite
 
     @Environment(\.dismiss) var dismiss
@@ -108,6 +108,6 @@ struct AddMuteItemView: View {
 
 struct AddMuteItemView_Previews: PreviewProvider {
     static var previews: some View {
-        AddMuteItemView(state: test_damus_state, new_text: .constant(""))
+        AddMuteItemView(state: test_damus_state)
     }
 }