sandbox.go: fix comment

Change-Id: Iacba4d6d75cac6b540bf855831873e35df47334f
Reviewed-on: https://go-review.googlesource.com/c/playground/+/465999
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
Run-TryBot: shuang cui <imcusg@gmail.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
TryBot-Bypass: Dmitri Shuralyov <dmitshur@google.com>

sandbox.go

diff --git a/sandbox.go b/sandbox.go
index 4f3ed9d..c081e06 100644
--- a/sandbox.go
+++ b/sandbox.go
@@ -242,7 +242,7 @@
 	return !unicode.IsLower(r)
 }
 
-// getTestProg returns source code that executes all valid tests and examples in src.
+// isTestProg returns source code that executes all valid tests and examples in src.
 // If the main function is present or there are no tests or examples, it returns nil.
 // getTestProg emulates the "go test" command as closely as possible.
 // Benchmarks are not supported because of sandboxing.