fix indentation

Author: ko1

test/console/backtrace_test.rb

@@ -189,7 +189,7 @@ def test_backtrace_prints_nested_block_label_correctly
     end
   end
 
-   class ThreadLockingTraceTest < ConsoleTestCase
+  class ThreadLockingTraceTest < ConsoleTestCase
     def program
       <<~RUBY
      1| th0 = Thread.new{sleep}