avutil/hmac: remove gap in AVHMACType enum values

Signed-off-by: James Almer <jamrial@gmail.com>

libavutil/hmac.h

@@ -35,7 +35,7 @@ enum AVHMACType {
     AV_HMAC_SHA1,
     AV_HMAC_SHA224,
     AV_HMAC_SHA256,
-    AV_HMAC_SHA384 = 12,
+    AV_HMAC_SHA384,
     AV_HMAC_SHA512,
 };