[Doc] Remove legacy protocol description

doc/markdown/architecture/protocol.md

@@ -151,46 +151,4 @@ Here is an example of a JSON control block:
 }
 ~~~
 
-Moreover, [UCL](https://github.com/vstakhov/libucl) json extensions and syntax conventions are also supported inside the control block.
-
-## Legacy RSPAMC protocol
-
-For compatibility, rspamd supports legacy `RSPAMC` and also SpamAssassin `SPAMC` protocols. Though their usage is discouraged, these protocols can still be used as a last resort to communicate with rspamd from legacy applications.
-
-The RSPAMC dialog looks as follows:
-
-~~~
-SYMBOLS RSPAMC/1.1
-Content-Length: 2200
-
-<message octets>
-
-RSPAMD/1.1 0 OK
-Metric: default; True; 10.40 / 10.00 / 0.00
-Symbol: R_UNDISC_RCPT
-Symbol: ONCE_RECEIVED
-Symbol: R_MISSING_CHARSET
-Urls:
-~~~
-
-The RSPAMC protocol also supports different commands:
-
-| Command | Description |
-| :-------| :----- |
-| CHECK   | Check a message and output results for each metric, but do not output symbols. |
-| SYMBOLS | Same as `CHECK`, but output symbols. |
-| PROCESS | Same as `SYMBOLS` but also output the original message with inserted X-Spam headers. |
-| PING    | Do not do any processing, just check rspamd state. |
-
-
-After the command, there should be one mandatory header - `Content-Length` - which defines a message's length in bytes, and optional headers (same as for HTTP).
-
-rspamd supports SpamAssassin's `spamc` protocol, and you can even pass rspamc headers in spamc mode, but the reply of rspamd in `spamc` mode is truncated to the "default" metric only with no options for symbols being displayed. Rspamc reply looks as follows: 
-
-	RSPAMD/1.1 0 OK
-	Metric: default; True; 10.40 / 10.00 / 0.00
-	Symbol: R_UNDISC_RCPT
-	Symbol: ONCE_RECEIVED
-	Symbol: R_MISSING_CHARSET
-	Urls: 
- 
+Moreover, [UCL](https://github.com/vstakhov/libucl) json extensions and syntax conventions are also supported inside the control block.