[bfops/csharp-ci]: try to fix workspace error

Author: bfops

demo/Blackholio/server-rust/Cargo.toml

@@ -5,6 +5,8 @@ edition = "2021"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
+[workspace]
+
 [lib]
 crate-type = ["cdylib"]