Had Ananias been told that believers are not under the Law but under grace?
No. Ananias had not been told that believers are not under the Law but under grace. The context describes him as a devout, law-keeping Jewish believer. No one had yet told these Jewish believers to quit temple worship or stop legalism. They maintained their Judaism while recognizing Jesus as the Christ.
Les directs attention to Acts chapter 22, where Paul recounts his conversion in the first person many years after the Damascus experience. There Ananias is described as a devout man according to the Word, a Jew. Les explains that Ananias was a believing but law-keeping Jew. No one had told Ananias yet, 'You're not under the Law, you're under grace.' No one had told these Jewish believers to quit temple worship or stop legalism. They had maintained their Judaism, yet they also recognized that Jesus was the Christ.
And when I could not see for the glory of that light, being led by the hand of them that were with me, I came into Damascus.