remove oxt.me as fee rates source

Author: craigraw

src/main/resources/com/sparrowwallet/sparrow/preferences/general.fxml

@@ -36,7 +36,6 @@
                         <FXCollections fx:factory="observableArrayList">
                             <FeeRatesSource fx:constant="ELECTRUM_SERVER" />
                             <FeeRatesSource fx:constant="MEMPOOL_SPACE" />
-                            <FeeRatesSource fx:constant="OXT_ME" />
                             <FeeRatesSource fx:constant="MINIMUM" />
                         </FXCollections>
                     </items>