Change one wording for Solana staking

[ghost]

🦒 Context (issues, jira)

Feedback coming from customer support:

SOL stacking is quite complex to understand from a customer POV. A super quick win in terms of UI would be to re-use the same wording.
For instance here, available balance doesn't have the same meaning in the delegation tab.

💻 Description / Demo (image or video)

Wording change validated by product: Withdrawable instead of Available balance.

🖤 Expectations to reach

PR must pass CI, rebase develop if conflicts. Thanks!

• on QA: at least one of these two checkboxes must be checked:
  • a specific test planned is defined on Jira
  • this PR is covered by automatic UI test
• on delivery: at least one of these two checkboxes must be checked:
  • Option 1: no impact: The changes of this PR have ZERO impact on the userland (invisible for users)
  • Option 2: atomic delivery: the changes is atomic and complete (no partial delivery)

[github-actions]

Thanks for your contribution.
To be able to merge in develop branch, you need to:

• pass the CI
• if needed, run /generate-screenshots
• have a dev review
• have a QA review
• if needed, /upgrade-llc

Why /generate-screenshots ?

If your PR contains UI related changes,
it might be necessary to regenerate screenshots.

Why /upgrade-llc ?

If your PR requires an update to the ledger-live-common library,
once the PR is merged on develop on ledger-live-common side,
you need to run /upgrade-llc to switch back to ledger-live-common@develop here before merging.

[github-actions]

Coverage report

St.❔	Category	Percentage	Covered / Total
🔴	Statements	23.46%	38/162
🔴	Branches	20.51%	8/39
🔴	Functions	3.64%	2/55
🔴	Lines	24.16%	36/149

Test suite run success

2 tests passing in 2 suites.

Report generated by 🧪jest coverage report action from 2cd29b1

[ghost]

/generate-screenshots

[github-actions]

Generating new screenshots