Drop 4M exclusion for headers

[roman-khimov]

Is your feature request related to a problem? Please describe.

I'm always frustrated when limits are not simple. #290 introduced an exclusion for already existing objects. Likely this can be removed.

Describe the solution you'd like

Flat 16K limit for everything.

Additional context

Once 0.41.0 is released and applied to all networks, create a checker tool, walk through stored objects and decide if we can do this.

[roman-khimov]

Aside from other objects discussed with their owners we've got only 8yTpBtJXnbhQF4jQxGgSrgzzyZXbk1Jy3gsxVKr2yEam/6fRSWE7WXCGMareoMmgmAnXp5br6SUetDYrczidLqriv that is problematic on mainnet. This will eventually be sorted out, so I think we can move on here.