chore: rm blockchain category due to category slugs are not currently…

… supported on crates.io (#63)

Co-authored-by: Alexandr Devyatkin <[email protected]>

Cargo.toml

@@ -16,7 +16,6 @@ keywords = [
     "cryptography",
 ]
 categories = [
-    "blockchain",
     "cryptography"
 ]
 repository = "https://github.com/wavesplatform/waves-rust"