b05ba16a05 ci: Remove serde version pinning (Tobin C. Harding)
Pull request description:
The MSRV break in serde is fixed now, remove the serde version pinning.
Fix: #1256
ACKs for top commit:
Kixunil:
ACK b05ba16a05 if CI passes.
apoelstra:
ACK b05ba16a05
Tree-SHA512: 2046b443500a848cb7b22576473f3b09ece4538dd3d30d7a06b09b28d6fe26f5c4d482f70ec0ec1b79469c221dc9c09e8b05b83debb71fd27f7dc30571cbbcfe