cmd/link: remove misleading comment

The comment suggests that the text section is briefly writable.
That is not the case. As the earlier part of the comment explains,
part of the text section is mapped twice, once r-x and once rw-.
It is never the case that there is writable executable memory.

Change-Id: I56841e19a8a08f2515f29752536a5c8f180ac8c9
Reviewed-on: https://go-review.googlesource.com/c/go/+/715622
Auto-Submit: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

Author: ianlancetaylor

src/cmd/link/internal/ld/data.go

@@ -2852,9 +2852,6 @@ func (ctxt *Link) address() []*sym.Segment {
 		// will be such that the last page of the text segment will be
 		// mapped twice, once r-x and once starting out rw- and, after
 		// relocation processing, changed to r--.
-		//
-		// Ideally the last page of the text segment would not be
-		// writable even for this short period.
 		va = uint64(Rnd(int64(va), *FlagRound))
 
 		order = append(order, &Segrodata)