cmd/pprof/internal: map/slice literals janitoring

Simplify slice/map literal expression.
Caught with gofmt -d -s, fixed with gofmt -w -s

Change-Id: I19723900d0649019bf79b9330d68525a68ed69c4
Reviewed-on: https://go-review.googlesource.com/13835Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/pprof/internal/profile/legacy_profile.go

@@ -589,7 +589,7 @@ func parseHeap(b []byte) (p *Profile, err error) {
 		p.Sample = append(p.Sample, &Sample{
 			Value:    value,
 			Location: sloc,
-			NumLabel: map[string][]int64{"bytes": []int64{blocksize}},
+			NumLabel: map[string][]int64{"bytes": {blocksize}},
 		})
 	}