Default value for min peers before starting sync from 5 to 1

[macfarla]

PR description

Change default value for minimum number of peers required before starting sync (only used by non-PoS networks) from 5 to 1.

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[matthew1001]

I think I'm in favour of this change. The enterprise-profile.toml already sets sync-min-peers to 1 so it makes sense to just change the default.

[matthew1001]

LGTM

[fab-10]

since it could make sense for private networks, for public ones that could increase the risk of syncing to the wrong fork, so could be possible to condition this on the basis if the network is public or private? probably looking at the presence or not of a custom genesis file?