chore: bump crate version

- 'mithril-signer' from '0.2.120' to '0.2.121'.

Author: jpraynaud

Cargo.lock

@@ -1,6 +1,6 @@
 [package]
 name = "mithril-signer"
-version = "0.2.120"
+version = "0.2.121"
 description = "A Mithril Signer"
 authors = { workspace = true }
 edition = { workspace = true }