Revert "qml: pressing "Esc" on desktop to ~simulate "back" button"

This reverts commit 7f7ee8d82f.

This commit caused a regression with the android back button not closing a dialog.

reproduce:
1. from the main window, press receive.
2. in the request details window, press Create request.
3. in the receive payment dialog, press Copy
4. observe dialog cannot be closed by back button

electrum/gui/qml/components/Pin.qml

@@ -23,7 +23,7 @@ ElDialog {
 
     focus: true
 
-    closePolicy: canCancel ? Popup.CloseOnPressOutside : Popup.NoAutoClose
+    closePolicy: canCancel ? Popup.CloseOnEscape | Popup.CloseOnPressOutside : Popup.NoAutoClose
 
     property bool canCancel: true
 

electrum/gui/qml/components/controls/ElDialog.qml

@@ -19,7 +19,7 @@ Dialog {
     }
 
     closePolicy: allowClose
-        ? Popup.CloseOnPressOutside
+        ? Popup.CloseOnEscape | Popup.CloseOnPressOutside
         : Popup.NoAutoClose
 
     onOpenedChanged: {

electrum/gui/qml/components/main.qml

@@ -439,14 +439,6 @@ ApplicationWindow
         }
     }
 
-    Shortcut {
-        context: Qt.ApplicationShortcut
-        sequence: "Esc"
-        onActivated: {
-            close()
-        }
-    }
-
     Connections {
         target: Daemon
         function onWalletRequiresPassword(name, path) {