Parity-ethereum: Increase Gas-floor-target on Kovan to 8000000

[retotrinkler]

_Before filing a new issue, please provide the following information._

I'm running:

• Which Parity version?: 1.9.3-beta-804ddfe-20180219/x86_64-linux-gnu/rustc1.24.0
• Which operating system?: Linux
• How installed?: via binaries
• Are you fully synchronized?: yes
• Which network are you connected to?: kovan
• Did you try to restart the node?: yes

_Your issue description goes here below. Try to include actual vs. expected behavior and steps to reproduce the issue._

actual

Gas-floor-target at 4700000

--gas-floor-target=[GAS]
    Amount of gas per block to target when sealing a new block. (default: 4700000)

expected

Gas-floor-target at 8000000 https://ethstats.net/

[5chdn]

Might be worth to bump the default for all networks to 8M.

[5chdn]

https://github.com/kovan-testnet/config/pull/8

[rphmeier]

Increase Gas-floor-target on Kovan to 8000000

changing network parameters only requires collaboration on the part of authorities, not changing client defaults.