runtime: fix file references in hiter's comments

The file "cmd/internal/gc/range.go" does not exist, but should be
"cmd/compile/internal/gc/range.go".

Change-Id: I26e5560b9d0b7eea8502c6b375e45fc87aed1276
GitHub-Last-Rev: 5f19dca
GitHub-Pull-Request: #42391
Reviewed-on: https://go-review.googlesource.com/c/go/+/267837
Reviewed-by: Ian Lance Taylor <[email protected]>
Trust: Emmanuel Odeke <[email protected]>

Author: veezhang

src/runtime/map.go

@@ -162,8 +162,8 @@ type bmap struct {
 // If you modify hiter, also change cmd/compile/internal/gc/reflect.go to indicate
 // the layout of this structure.
 type hiter struct {
-	key         unsafe.Pointer // Must be in first position.  Write nil to indicate iteration end (see cmd/internal/gc/range.go).
-	elem        unsafe.Pointer // Must be in second position (see cmd/internal/gc/range.go).
+	key         unsafe.Pointer // Must be in first position.  Write nil to indicate iteration end (see cmd/compile/internal/gc/range.go).
+	elem        unsafe.Pointer // Must be in second position (see cmd/compile/internal/gc/range.go).
 	t           *maptype
 	h           *hmap
 	buckets     unsafe.Pointer // bucket ptr at hash_iter initialization time