build(deps): bump bitcoin from 0.29.2 to 0.31.0

Bumps [bitcoin](https://github.com/rust-bitcoin/rust-bitcoin) from 0.29.2 to 0.31.0.
- [Release notes](https://github.com/rust-bitcoin/rust-bitcoin/releases)
- [Commits](rust-bitcoin/rust-bitcoin@0.29.2...bitcoin-0.31.0)

---
updated-dependencies:
- dependency-name: bitcoin
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Cargo.toml

@@ -19,7 +19,7 @@ lightning-background-processor = { git = "https://github.com/fiksn/rust-lightnin
 lightning-rapid-gossip-sync = { git = "https://github.com/fiksn/rust-lightning" }
 base64 = "0.21.3"
 # do not upgrade to bitcoon 0.30!
-bitcoin = "0.29.2"
+bitcoin = "0.31.0"
 bitcoin-bech32 = "0.13.0"
 bech32 = "0.9.1"
 hex = "0.4.3"