xtask: do not release

xtask/Cargo.toml

@@ -1,10 +1,12 @@
 [package]
 name = "xtask"
+publish = false
 version = "0.1.0"
 edition = "2018"
 
-# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
-
 [dependencies]
 structopt = {version = "0.3", default-features = false }
-anyhow = "1"
+anyhow = "1"
+
+[package.metadata.release]
+release = false