cmd/compile/internal/ir: fix up stale comment

Fix a small stale comment in FinishCaptureNames (refers to old code
structure before the big refactoring).

Change-Id: I2dfb84ce238f919f6e17061439a8bd9b09459dae
Reviewed-on: https://go-review.googlesource.com/c/go/+/296829
Trust: Than McIntosh <thanm@google.com>
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

Author: thanm

src/cmd/compile/internal/ir/name.go

@@ -398,7 +398,7 @@ func FinishCaptureNames(pos src.XPos, outerfn, fn *Func) {
 	// unhook them.
 	// make the list of pointers for the closure call.
 	for _, cv := range fn.ClosureVars {
-		// Unlink from n; see comment in syntax.go type Param for these fields.
+		// Unlink from n; see comment above on type Name for these fields.
 		n := cv.Defn.(*Name)
 		n.Innermost = cv.Outer