time: fix a typo in comments

Change-Id: I407d7215d077176678a714ff1446e987bb818f7c
GitHub-Last-Rev: 22012adb3a8dada5b19eba6d6a9b067295a306a7
GitHub-Pull-Request: golang/go#31988
Reviewed-on: https://go-review.googlesource.com/c/go/+/176797
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/time/time.go

@@ -940,7 +940,7 @@ overflow:
 func Since(t Time) Duration {
 	var now Time
 	if t.wall&hasMonotonic != 0 {
-		// Common case optimization: if t has monotomic time, then Sub will use only it.
+		// Common case optimization: if t has monotonic time, then Sub will use only it.
 		now = Time{hasMonotonic, runtimeNano() - startNano, nil}
 	} else {
 		now = Now()
@@ -953,7 +953,7 @@ func Since(t Time) Duration {
 func Until(t Time) Duration {
 	var now Time
 	if t.wall&hasMonotonic != 0 {
-		// Common case optimization: if t has monotomic time, then Sub will use only it.
+		// Common case optimization: if t has monotonic time, then Sub will use only it.
 		now = Time{hasMonotonic, runtimeNano() - startNano, nil}
 	} else {
 		now = Now()