Find and replace all nolint instances refering to the `lll` linter and
replace with `ll` which is the name of our custom version of the `lll`
linter which can be used to ignore log lines during linting.
The next commit will do the configuration of the custom linter and
disable the default one.
A new top level feeurl option was added recently to replace the neutrino.feeurl
option. The new option was never added to the sample config file and the
text was never updated to reflect that the option is required for
neutrino on mainnet. We fix this and also add a valid mainnet example
URL to the sample config file.
