Small improvement in startup logs

[MarekM25]

Changes

• Removed the ugly log ⬇️
  
  It was duplicated with https://github.com/NethermindEth/nethermind/blob/master/src/Nethermind/Nethermind.Blockchain/BlockTree.cs#L216
• Don't print BeaconPivot when it is null
• Changed one Warn to Info

Types of changes

What types of changes does your code introduce?

• Bugfix (a non-breaking change that fixes an issue)
• New feature (a non-breaking change that adds functionality)
• Breaking change (a change that causes existing functionality not to work as expected)
• Optimization
• Refactoring
• Documentation update
• Build-related changes
• Other: logs-related changes

Testing

Requires testing

• Yes
• No

If yes, did you write tests?

• Yes
• No

Notes on testing

I've run unsynced/synced nodes a few times. Of course, there is no need to sync the node to test it.