[Rspamd] Remove deprecated attachments_only in AV module

[Rspamd] Remove old symbol score

data/conf/rspamd/local.d/antivirus.conf

@@ -1,5 +1,5 @@
 clamav {
-  attachments_only = true;
+  scan_mime_parts = true;
   symbol = "CLAM_VIRUS";
   type = "clamav";
   log_clean = true;