cmd/releasebot: fix a typo in a document string

For golang/go#45998

Change-Id: I411e0ae3bdc9d0537ccc9115f7169e39dd279157
Reviewed-on: https://go-review.googlesource.com/c/build/+/319352
Trust: Carlos Amedee <carlos@golang.org>
Run-TryBot: Carlos Amedee <carlos@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

cmd/releasebot/main.go

@@ -569,8 +569,7 @@ func (w *Work) postSummary() {
 	}
 
 	// Ensure that the entire body can be posted to the issue by splitting it into multiple
-	// GitHub comments if necesary.
-	// golang.org/issue/45998
+	// GitHub comments if necessary. See golang.org/issue/45998.
 	bodyParts := splitLogMessage(body, githubCommentCharacterLimit)
 	for _, b := range bodyParts {
 		err := postGithubComment(w.ReleaseIssue, b)