Make 2nd file download async to fix (#9711)

# Addresses #9680 
- Add 100ms timeout before 2nd key is downloaded from browser
- Fix file decoding to correctly download both keys
- Fix copy

# Checklist for submitter

- [x] Manual QA for all new/changed functionality

Co-authored-by: Jacob Shandling <jacob@fleetdm.com>
Co-authored-by: Roberto Dip <roberto@fleetdm.com>

frontend/pages/admin/IntegrationsPage/cards/Mdm/Mdm.tsx

@@ -105,7 +105,7 @@ const Mdm = (): JSX.Element => {
 
       const privateFilename = "fleet-apple-mdm-bm-private.key";
       const privateFile = new global.window.File(
-        [keys.decodedPublic],
+        [keys.decodedPrivate],
         privateFilename,
         {
           type: "application/x-pem-file",
@@ -113,7 +113,9 @@ const Mdm = (): JSX.Element => {
       );
 
       FileSaver.saveAs(publicFile);
-      FileSaver.saveAs(privateFile);
+      setTimeout(() => {
+        FileSaver.saveAs(privateFile);
+      }, 100);
     } else {
       renderFlash(
         "error",