fix: run cmd in readme [skip ci]

[colinlyguo]

Hey, team, when I'm running the service locally, using ./skandha would encounter a non-existent optional parameters error, the log indicates there is at least one parameter. While I tried ./skandha standalone and it works, it's also consistent with this video in readme: https://www.youtube.com/watch?v=O0_lm7b0GXE.

Thus submitting this PR to fix this.

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)
• Documentation Update
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Other (please describe):