Avoid the backup file picker adding .zip

We were setting the MIME type of the intent to select the backup file to
application/zip. This made the resulting file end up with .gnca.zip
extension.

Author: rivaldi8

app/src/main/java/org/gnucash/android/ui/settings/BackupPreferenceFragment.java

@@ -175,7 +175,7 @@ public boolean onPreferenceClick(Preference preference) {
 
 		if (key.equals(getString(R.string.key_backup_location))){
 			Intent createIntent = new Intent(Intent.ACTION_CREATE_DOCUMENT);
-			createIntent.setType("application/zip");
+			createIntent.setType("*/*");
 			createIntent.addCategory(Intent.CATEGORY_OPENABLE);
 			String bookName = BooksDbAdapter.getInstance().getActiveBookDisplayName();
 			createIntent.putExtra(Intent.EXTRA_TITLE, Exporter.sanitizeFilename(bookName)+ "_" + getString(R.string.label_backup_filename));