qml: introduction text bottom margins in RbF bump fee and cancel dialogs

electrum/gui/qml/components/RbfBumpFeeDialog.qml

@@ -47,6 +47,7 @@ ElDialog {
                 Label {
                     Layout.columnSpan: 2
                     Layout.fillWidth: true
+                    Layout.bottomMargin: constants.paddingLarge
                     text: qsTr('Increase your transaction\'s fee to improve its position in the mempool')
                     wrapMode: Text.Wrap
                 }

electrum/gui/qml/components/RbfCancelDialog.qml

@@ -44,6 +44,7 @@ ElDialog {
                 Label {
                     Layout.columnSpan: 2
                     Layout.fillWidth: true
+                    Layout.bottomMargin: constants.paddingLarge
                     text: qsTr('Cancel an unconfirmed RBF transaction by double-spending its inputs back to your wallet with a higher fee.')
                     wrapMode: Text.Wrap
                 }