runtime: amend comments a bit

Change-Id: I3cabc57f6b8f803f966221f9583a5edb8828ca12
GitHub-Last-Rev: 57569ace50
GitHub-Pull-Request: golang/go#76086
Reviewed-on: https://go-review.googlesource.com/c/go/+/715600
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Jorropo <jorropo.pgm@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@google.com>

src/runtime/defer_test.go

@@ -150,7 +150,7 @@ func TestAbortedPanic(t *testing.T) {
 // This tests that recover() does not succeed unless it is called directly from a
 // defer function that is directly called by the panic.  Here, we first call it
 // from a defer function that is created by the defer function called directly by
-// the panic.  In
+// the panic.
 func TestRecoverMatching(t *testing.T) {
 	defer func() {
 		r := recover()

src/runtime/runtime2.go

@@ -1352,7 +1352,7 @@ var (
 	// be atomic. Length may change at safe points.
 	//
 	// Each P must update only its own bit. In order to maintain
-	// consistency, a P going idle must the idle mask simultaneously with
+	// consistency, a P going idle must set the idle mask simultaneously with
 	// updates to the idle P list under the sched.lock, otherwise a racing
 	// pidleget may clear the mask before pidleput sets the mask,
 	// corrupting the bitmap.