Reduce configuration options

[eliska-n]

I found asab-iris still needs this configuration:

[web]
listen=0.0.0.0 8066
body_max_size=31457280       <--

Is it still valid? I remember we hot-fixed problems with big e-mails with this configuration.
If it is an acceptable solution, it should become a default configuration.
If not, this must be solved some other way.
Do not make a proper functionality of asab-iris to be dependent on enigmatic configuration.

[ateska]

This is a default, you don't need to specify it implicitly.

asab-iris/asabiris/app.py

Line 34 in 53858b0

"body_max_size": 31457280 # maximum size of the request body that the web server can handle.