fix(lute): fix signedTxns reconstruction

[acfunk]

Description

There was a bug in the construction of signedTxns where it was expecting result to only contain txns that the wallet signed. Lute's response has the same length as the request, so shift() was not appropriate - a simple index on result will do.

Checklist

Please, make sure to comply with the checklist below before expecting review

• Code compiles correctly
• Created tests which fail without the change (if possible)
• All tests passing
• Extended the README / documentation, if necessary