Don't wrap loop around waitpid call

Process.waitpid by default waits for its child to exit. So there's no
need to wrap a loop around it.

What happens in #485 is that the loop keeps running until it's killed by
puma with a `KILL` signal.

Reference: https://rubyapi.org/3.1/o/process#method-c-waitpid

Author: st0012

lib/debug/local.rb

@@ -98,7 +98,7 @@ def after_fork_parent
           # only check child process from its parent
           begin
             # wait for all child processes to keep terminal
-            loop{ Process.waitpid }
+            Process.waitpid
           rescue Errno::ESRCH, Errno::ECHILD
           end
         end