(query assist) revert removing backticks (#1896)

Signed-off-by: Joshua Li <joshuali925@gmail.com>
(cherry picked from commit b99920d)
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

server/routes/query_assist/routes.ts

@@ -77,7 +77,6 @@ export function registerQueryAssistRoutes(router: IRouter) {
  .replace(/[\r\n]/g, ' ')
  .trim()
  .replace(/ISNOTNULL/g, 'isnotnull') // https://github.com/opensearch-project/sql/issues/2431
- .replace(/`/g, '') // https://github.com/opensearch-project/dashboards-observability/issues/509, https://github.com/opensearch-project/dashboards-observability/issues/557
  .replace(/\bSPAN\(/g, 'span('); // https://github.com/opensearch-project/dashboards-observability/issues/759
  return response.ok({ body: ppl });
  } catch (error) {