Remove unused variable to suppress warning (#2388) [ci skip]

```
sample/observ.rb:30: warning: assigned but unused variable - clock
```

1 files changed, 1 insertions, 1 deletions

diff --git a/sample/observ.rb b/sample/observ.rb
index a7ea45271d..ef4a9f60f5 100644
--- a/sample/observ.rb
+++ b/sample/observ.rb
@@ -27,5 +27,5 @@ class Clock
   end
 end
 
-clock = Clock.new(Tick.new)
+Clock.new(Tick.new)
 sleep