runtime: tweak wording for doc

Change-Id: Id0be4b8744ded98cd28f94d89898d8cbac0f543e
GitHub-Last-Rev: e8a610e
GitHub-Pull-Request: #76197
Reviewed-on: https://go-review.googlesource.com/c/go/+/718420
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@golang.org>

Author: callthingsoff

src/runtime/mem.go

@@ -19,7 +19,7 @@ import "unsafe"
 //               fault, may give back unexpected zeroes, etc.).
 // 4) Ready - may be accessed safely.
 //
-// This set of states is more than is strictly necessary to support all the
+// This set of states is more than strictly necessary to support all the
 // currently supported platforms. One could get by with just None, Reserved, and
 // Ready. However, the Prepared state gives us flexibility for performance
 // purposes. For example, on POSIX-y operating systems, Reserved is usually a