DOC: correct typo in alert message about rspirep

This message comes when we run:
haproxy -c -V -f /etc/haproxy/haproxy.cfg
[ALERT] 072/233727 (30865) : parsing [/etc/haproxy/haproxy.cfg:34] : The 'rspirep' directive is not supported anymore sionce HAProxy 2.1. Use 'http-response replace-header' instead.
[ALERT] 072/233727 (30865) : Error(s) found in configuration file : /etc/haproxy/haproxy.cfg
[ALERT] 072/233727 (30865) : Fatal errors found in configuration.
diff --git a/src/cfgparse-listen.c b/src/cfgparse-listen.c
index 5079800..9bffee5 100644
--- a/src/cfgparse-listen.c
+++ b/src/cfgparse-listen.c
@@ -3867,7 +3867,7 @@
 		goto out;
 	}
 	else if (!strcmp(args[0], "rspirep")) {  /* replace response header from a regex ignoring case */
-	       ha_alert("parsing [%s:%d] : The '%s' directive is not supported anymore sionce HAProxy 2.1. "
+	       ha_alert("parsing [%s:%d] : The '%s' directive is not supported anymore since HAProxy 2.1. "
 			"Use 'http-response replace-header' instead.\n", file, linenum, args[0]);
 		err_code |= ERR_ALERT | ERR_FATAL;
 		goto out;