fix: fix code

Author: oowl

t/01-pdk/08-response/05-set_header.t

@@ -138,7 +138,7 @@ invalid header value in array "foo": got table, expected string
 --- request
 GET /t
 --- response_body chop
-invalid header value for "foo": got nil, expected table, string, number or boolean
+invalid header value for "foo": got nil, expected array of string, string, number or boolean
 --- no_error_log
 [error]
 

t/01-pdk/08-response/06-add_header.t

@@ -137,7 +137,7 @@ invalid header value in array "foo": got table, expected string
 --- request
 GET /t
 --- response_body chop
-invalid header value for "foo": got nil, expected table, string, number or boolean
+invalid header value for "foo": got nil, expected array of string, string, number or boolean
 --- no_error_log
 [error]