MM-46577: Remove empty translation strings (#20876)

We replace the empty translation key with <untranslated>
which is ignored by the translation check tool.

https://mattermost.atlassian.net/browse/MM-46577

```release-note
NONE
```

app/admin.go

@@ -255,29 +255,29 @@ func (a *App) GetLatestVersion(latestVersionUrl string) (*model.GithubReleaseInf
 
 	res, err := http.Get(latestVersionUrl)
 	if err != nil {
-		return nil, model.NewAppError("GetLatestVersion", "app.admin.latest_version_external_error.failure", nil, "", http.StatusInternalServerError)
+		return nil, model.NewAppError("GetLatestVersion", model.NoTranslation, nil, "", http.StatusInternalServerError).Wrap(err)
 	}
 
 	defer res.Body.Close()
 
 	responseData, err := io.ReadAll(res.Body)
 	if err != nil {
-		return nil, model.NewAppError("GetLatestVersion", "app.admin.latest_version_read_all.failure", nil, "", http.StatusInternalServerError)
+		return nil, model.NewAppError("GetLatestVersion", model.NoTranslation, nil, "", http.StatusInternalServerError).Wrap(err)
 	}
 
 	var releaseInfoResponse *model.GithubReleaseInfo
 	err = json.Unmarshal(responseData, &releaseInfoResponse)
 	if err != nil {
-		return nil, model.NewAppError("GetLatestVersion", "app.admin.latest_version_unmarshal.failure", nil, "", http.StatusInternalServerError)
+		return nil, model.NewAppError("GetLatestVersion", model.NoTranslation, nil, "", http.StatusInternalServerError).Wrap(err)
 	}
 
 	if validErr := releaseInfoResponse.IsValid(); validErr != nil {
-		return nil, model.NewAppError("GetLatestVersion", "app.admin.latest_version_external_error.failure", nil, "", http.StatusInternalServerError)
+		return nil, model.NewAppError("GetLatestVersion", model.NoTranslation, nil, "", http.StatusInternalServerError).Wrap(validErr)
 	}
 
 	err = latestVersionCache.Set("latest_version_cache", releaseInfoResponse)
 	if err != nil {
-		return nil, model.NewAppError("GetLatestVersion", "app.admin.latest_version_set_cache.failure", nil, "", http.StatusInternalServerError)
+		return nil, model.NewAppError("GetLatestVersion", model.NoTranslation, nil, "", http.StatusInternalServerError).Wrap(err)
 	}
 
 	return releaseInfoResponse, nil