Also say "Connect ..." on remaining key backup buttons

This updates the remaining buttons shown when a backup exists but is not trusted
so that they all now say "Connect this device to Key Backup" instead of "Use Key
Backup".

This is a follow up to matrix-org#2917
and was agreed with Riot iOS team
element-hq/element-ios#2375 (comment).

Fixes element-hq/element-web#9542

src/components/views/dialogs/LogoutDialog.js

@@ -130,7 +130,7 @@ export default class LogoutDialog extends React.Component {
                 const DialogButtons = sdk.getComponent('views.elements.DialogButtons');
                 let setupButtonCaption;
                 if (this.state.backupInfo) {
-                    setupButtonCaption = _t("Use Key Backup");
+                    setupButtonCaption = _t("Connect this device to Key Backup");
                 } else {
                     // if there's an error fetching the backup info, we'll just assume there's
                     // no backup for the purpose of the button caption

src/components/views/rooms/RoomRecoveryReminder.js

@@ -119,7 +119,7 @@ export default class RoomRecoveryReminder extends React.PureComponent {
 
         let setupCaption;
         if (this.state.backupInfo) {
-            setupCaption = _t("Use Key Backup");
+            setupCaption = _t("Connect this device to Key Backup");
         } else {
             setupCaption = _t("Start using Key Backup");
         }

src/i18n/strings/en_EN.json

@@ -822,7 +822,6 @@
     "%(roomName)s is not accessible at this time.": "%(roomName)s is not accessible at this time.",
     "Try again later, or ask a room admin to check if you have access.": "Try again later, or ask a room admin to check if you have access.",
     "%(errcode)s was returned while trying to access the room. If you think you're seeing this message in error, please <issueLink>submit a bug report</issueLink>.": "%(errcode)s was returned while trying to access the room. If you think you're seeing this message in error, please <issueLink>submit a bug report</issueLink>.",
-    "Use Key Backup": "Use Key Backup",
     "Never lose encrypted messages": "Never lose encrypted messages",
     "Messages in this room are secured with end-to-end encryption. Only you and the recipient(s) have the keys to read these messages.": "Messages in this room are secured with end-to-end encryption. Only you and the recipient(s) have the keys to read these messages.",
     "Securely back up your keys to avoid losing them. <a>Learn more.</a>": "Securely back up your keys to avoid losing them. <a>Learn more.</a>",