fix

Author: saethlin

tests/ui/panics/default-backtrace-ice.stderr

@@ -7,8 +7,10 @@ LL | fn main() { missing_ident; }
 
 aborting due to `-Z treat-err-as-bug=1`
 stack backtrace:
-      [... omitted 2 frames ...]
-
+(end_short_backtrace)
+(begin_short_backtrace)
+(end_short_backtrace)
+(begin_short_backtrace)
 
 error: the compiler unexpectedly panicked. this is a bug.