internal/screentest: fix function name in comment

Change-Id: I55dfed6ab5e87794d992519d2916080d9d60fe0f
Reviewed-on: https://go-review.googlesource.com/c/website/+/579197
Reviewed-by: qiu laidongfeng2 <2645477756@qq.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Run-TryBot: shuang cui <imcusg@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
diff --git a/internal/screentest/screentest.go b/internal/screentest/screentest.go
index 29df1df..fe89681 100644
--- a/internal/screentest/screentest.go
+++ b/internal/screentest/screentest.go
@@ -344,7 +344,7 @@
 	return client.Close()
 }
 
-// cleanBkts ensures the set of directories in dirs exists and
+// cleanDirs ensures the set of directories in dirs exists and
 // clears dirs of all files not included in the set of keepFiles.
 func cleanDirs(dirs, keepFiles, safeExts map[string]bool) error {
 	for dir := range dirs {