wendelin: There is no need for Products.signalstack

Zope integrated Products.signalstack back in 2010:

    https://github.com/zopefoundation/Zope/commit/16796274
    ( Integrated the Products.signalstack / z3c.deadlockdebugger
      packages. You can now send a SIGUSR1 signal to a Zope process and get a
      stack trace of all threads printed out on the console. This works even
      if all threads are stuck. )

In 404150b7 (wendelin: Teach -dev build to dump all threads traceback on
SIGUSR1) it was my mistake to add Products.signalstack.

/reviewed-by TrustMe
/cc @Tyagov

software/wendelin/software-dev.cfg

@@ -11,7 +11,3 @@ parts += wendelin.core-dev
 # tell erp5 to use -dev eggs instead of released ones
 eggs -= ${wendelin.core:egg}
 eggs += ${wendelin.core-dev:egg}
-
-# kill -USR1 <runzope-pid>    ->  traceback of all threads -> stdout
-#                                 ( logged to slappartX/.slappartX_zope-Y.log )
-        Products.signalstack