Revert changes for high fixed gas prices

[konradkonrad]

Description

During the Bespin release candidate testing, we switched the SP CI setups to use a fixed gas price setting of a rather high 500 gwei. (See https://github.com/raiden-network/scenario-player/pull/679/files).
This, paired with an increased node funding, was meant to reduce failure noise that originated in weird gas price fluctuations in the goerli network.

Since this is neither a realistic test setup, nor a sustainable way to operate the scenario player (we'd run out of goerliETH quite soon), we need to roll back these changes and come up with more reasonable solutions (see also raiden-network/raiden#7095).

The current change is activated through adjusting the variable

- SP_BRANCH=develop
+ SP_BRANCH=higher_funding

in /var/lib/scenario-player/env.sh on both SP CI servers.

Due to the related changes in raiden-network/raiden#7087 and raiden-network/raiden#7088 we may also have to adjust the default environments in this repository.

[konradkonrad]

@ezdac please add anything I may have missed above!

[karlb]

Due to the related changes in raiden-network/raiden#7087 and raiden-network/raiden#7088 we may also have to adjust the default environments in this repository.

I fixed that with d5e863e, already.