Minor clarifications in staking as delegators procedures

[saniksin]

Description of the Changes

Clarified the difference between enter_delegation_pool and add_to_delegation_pool functions in the staking documentation.

• Specified that enter_delegation_pool should be used when a user delegates for the first time to a pool.
• Explained that add_to_delegation_pool is intended for adding more tokens after the initial delegation.

These changes aim to eliminate confusion between the two similar-sounding functions and help users avoid mistakes when interacting with the delegation contract.

PR Preview URL

https://starknet-io.github.io/starknet-docs/pr-1692/architecture/staking/#staking_as_delegators

Check List

• Changes made against main branch and PR does not conflict
• PR title is meaningful, e.g: clarify usage of delegation pool entry functions
• Detailed description added under "Description of the Changes"
• Specific URL(s) added under "PR Preview URL"

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This change is 

[starknet-bot]

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[LandauRaz]

Thanks for the contribution, @saniksin!

[starknet-bot]

Your preview build is ready! ✨ Check the following link in 1-2 minutes: https://starknet-io.github.io/starknet-docs/pr-1692/ .

[starknet-bot]

Your preview build is ready! ✨ Check the following link in 1-2 minutes: https://starknet-io.github.io/starknet-docs/pr-1692/ .