post303.d: clarify that this is an RFC violation

... and not the other way around, which this previously said.

Reported-by: Vasiliy Faronov
Fixes #2723
Closes #2726

docs/cmdline-opts/post303.d

@@ -4,8 +4,7 @@ Protocols: HTTP
 See-also: post302 post301 location
 Added: 7.26.0
 ---
-Tells curl to respect RFC 7231/6.4.4 and not convert POST requests into GET
-requests when following a 303 redirection. The non-RFC behaviour is ubiquitous
-in web browsers, so curl does the conversion by default to maintain
-consistency. However, a server may require a POST to remain a POST after such
-a redirection. This option is meaningful only when using --location.
+Tells curl to violate RFC 7231/6.4.4 and not convert POST requests into GET
+requests when following 303 redirections. A server may require a POST to
+remain a POST after a 303 redirection. This option is meaningful only when
+using --location.