release: bump slog-json version to 2.5.0

This release includes a relicensing to MPL-2.0 OR MIT OR Apache-2.0.

Author: Ryan Lopopolo

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "slog-json"
-version = "2.4.0"
+version = "2.5.0"
 edition = "2018"
 authors = ["Dawid Ciężarkiewicz <dpc@dpc.pw>"]
 description = "JSON drain for slog-rs"