Update sqlx to 0.8.6 to fix security vulnerability
Fixes GHSA-xmrp-424f-vfpx (CVE for protocol-level SQL injection)
The vulnerability affects sqlx <= 0.8.0 where encoding values larger
than 4GiB can cause the length prefix in the protocol to overflow.
Updated from 0.7.4 to 0.8.6 which includes the fix.