doc: Update Sedge-Lido guide

[AntiD2ta]

Changes:

• Update 'Staking with Lido using Sedge' guide

• Types of changes

What types of changes does your code introduce? Put an x in the boxes that apply

• [ ] Bugfix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [X] Documentation Update
• [ ] Code style update (formatting, renaming)
• [ ] Refactoring (no functional changes, no api changes)
• [ ] Build related changes
• [ ] Other (please describe):

Testing

Requires testing

• [ ] Yes
• [X] No

In case you checked yes, did you write tests?

• [ ] Yes
• [ ] No

Further comments

Instructions for importing existing keys will be added later.