Fix typo in package name. NFC

src/sys/flock_other.go

@@ -1,6 +1,6 @@
 //go:build !unix
 
-package os
+package sys
 
 import (
 	"fmt"

src/sys/flock_posix.go

@@ -1,6 +1,6 @@
 //go:build unix
 
-package os
+package sys
 
 import (
 	"os"

src/sys/signal.go

@@ -2,7 +2,7 @@
 // will do on Windows (tl;dr nothing calls the reload handler, the interrupt handler works
 // more or less how you'd expect).
 
-package os
+package sys
 
 import (
 	"os"