Upgrade openhands-aci to 0.2.6

[ryanhoangt]

• This change is worth documenting at https://docs.all-hands.dev/
• Include this change in the Release Notes. If checked, you must provide an end-user friendly description for your change below

Fix CWD path suggestions for agent from openhands-aci;
Fix error when reading file with encoding other than utf-8.

End-user friendly description of the problem this fixes or functionality that this introduces.

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Give a summary of what the PR does, explaining any non-trivial design decisions.

This PR updates openhands-aci to 0.2.6 that fixes:

• CWD path suggestions for openhands-aci
• Error when reading file with encoding other than utf-8

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Link of any specific issues this addresses.

Close #7139
Close #7174