Adapt existing enum regression test for underlying type specification feature

Author: danpoe

regression/ansi-c/enum9/test.desc

@@ -3,8 +3,6 @@ main.c
 --verbosity 2
 ^EXIT=0$
 ^SIGNAL=0$
-(main.c:1:\d+)|(main.c\(1\)): warning: ignoring specification of underlying type for enum
-(main.c:6:\d+)|(main.c\(6\)): warning: ignoring specification of underlying type for enum
 (main.c:13:\d+)|(main.c\(13\)): warning: ignoring specification of underlying type for enum
 (main.c:14:\d+)|(main.c\(14\)): warning: ignoring specification of underlying type for enum
 (main.c:19:\d+)|(main.c\(19\)): warning: ignoring specification of underlying type for enum