Adjust core -p2 patch level

[geek-merlin]

Now that cweagans/composer-patches allows it, we should adjust the core patch level by default.

[milkovsky]

Will the core patches be always applied wrong(with b, core assets) without this setting?

[milkovsky]

Ok, the answer on my question is -"yes". We definitely need to add this default.

[webflo]

Done in #418