os: enable TestFifoEOF on openbsd

The test successfully runs on currently supported versions (6.8 and
6.9) of openbsd.

Fixes #25877

Change-Id: I2694f08c5596b486453c2ac829f17b8bc455f828
Reviewed-on: https://go-review.googlesource.com/c/go/+/329732
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Trust: Tobias Klauser <tobias.klauser@gmail.com>
diff --git a/src/os/fifo_test.go b/src/os/fifo_test.go
index 9b262f8..007ed29 100644
--- a/src/os/fifo_test.go
+++ b/src/os/fifo_test.go
@@ -26,9 +26,6 @@
 	switch runtime.GOOS {
 	case "android":
 		t.Skip("skipping on Android; mkfifo syscall not available")
-	case "openbsd":
-		// On OpenBSD 6.2 this test just hangs for some reason.
-		t.Skip("skipping on OpenBSD; issue 25877")
 	}
 
 	dir := t.TempDir()