traceutil: fix gci import formatting in trace_test.go

gofmt expects 1-space minimum between the longest struct field name
and its type; the notExpectedMsg field (14 chars) was padded with
2 spaces, shifting all fields off by one. Reduced to 1-space minimum
so all types align at column 15.

Signed-off-by: Andrew Liu <andrewjliu22@gmail.com>