test/scheduler: suppress warnings

https://rubyci.s3.amazonaws.com/debian/ruby-master/log/20200514T123004Z.log.html.gz

```
/home/chkbuild/chkbuild/tmp/build/20200514T123004Z/ruby/test/scheduler/scheduler.rb:29: warning: assigned but unused variable - fiber
/home/chkbuild/chkbuild/tmp/build/20200514T123004Z/ruby/test/scheduler/scheduler.rb:156: warning: method redefined; discarding old fiber
/home/chkbuild/chkbuild/tmp/build/20200514T123004Z/ruby/test/scheduler/test_fiber.rb:27: warning: ambiguous first argument; put parentheses or a space even after `/' operator
```

2 files changed, 2 insertions, 4 deletions

diff --git a/test/scheduler/scheduler.rb b/test/scheduler/scheduler.rb
index b2d36cc728..820f441dcd 100644
--- a/test/scheduler/scheduler.rb
+++ b/test/scheduler/scheduler.rb
@@ -18,15 +18,13 @@ class Scheduler
     @ios = ObjectSpace::WeakMap.new
   end
 
-  attr :fiber
-
   attr :readable
   attr :writable
   attr :waiting
   attr :blocking
 
   def next_timeout
-    fiber, timeout = @waiting.min_by{|key, value| value}
+    _fiber, timeout = @waiting.min_by{|key, value| value}
 
     if timeout
       offset = timeout - current_time
diff --git a/test/scheduler/test_fiber.rb b/test/scheduler/test_fiber.rb
index 3452591cd9..368065016e 100644
--- a/test/scheduler/test_fiber.rb
+++ b/test/scheduler/test_fiber.rb
@@ -24,6 +24,6 @@ class TestSchedulerFiber < Test::Unit::TestCase
     thread.join
 
     assert_not_empty scheduler.blocking
-    assert_match /test_fiber.rb:\d+:in `close'/, scheduler.blocking.last
+    assert_match(/test_fiber\.rb:\d+:in `close'/, scheduler.blocking.last)
   end
 end