Bump lightning-block-sync version number to fix SemVer CI

PR lightningdevkit#4175 made the first breaking API change in `lightning-block-sync`
since v0.2 without bumping the version number. Here we bump the version
number, allowing our SemVer CI check to be happy again.

Author: tnull

lightning-block-sync/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "lightning-block-sync"
-version = "0.2.0+git"
+version = "0.3.0+git"
 authors = ["Jeffrey Czyz", "Matt Corallo"]
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/lightningdevkit/rust-lightning"