Update vulpemventures/electrs

[harshjv]

First of all thank you for Nigiri and docker images. We've been using them quite extensively in @liquality.

Recently, electrs added support for median blocktime via Blockstream/electrs@78adcdb, and we are looking forward to using it in our tests.

Will you be able to trigger a build on docker hub for vulpemventures/electrs?

Thanks 🙏