[test] fix failed tests in apicast-policy-ip-check.t

Previously, header contains space or control character were
considered invalid and were ignore by default. But in nginx
1.21.1, it now always returns an error instead if spaces or
control characters are used in a header

Author: tkan145

t/apicast-policy-ip-check.t

@@ -360,6 +360,8 @@ is always the valid one.
 [403, 200]
 
 === TEST 11: X-forwarded-for header with invalid data
+From 1.21.1, nginx will always returns an error if spaces or control
+characters are used in a header name
 --- configuration
 {
   "services": [
@@ -385,11 +387,9 @@ is always the valid one.
 }
 --- request
 GET /
---- response_body
-IP address not allowed
 --- more_headers eval
 X-forwarded-for: ,9.9.9.9
---- error_code: 403
+--- error_code: 400
 --- no_error_log
 [error]
 
@@ -420,10 +420,8 @@ X-forwarded-for: ,9.9.9.9
 }
 --- request
 GET /
---- response_body
-IP address not allowed
 --- more_headers eval
 X-forwarded-for: ,
---- error_code: 403
+--- error_code: 400
 --- no_error_log
 [error]