Unpin once_cell dependency and set MSRV to 1.56

Cargo.toml

@@ -9,26 +9,16 @@ license = "Apache-2.0 OR MIT"
 repository = "https://github.com/foresterre/storyteller"
 
 exclude = ["/.github", "docs/sketches/*.png"]
-
-[package.metadata]
-msrv = "1.38"
+rust-version = "1.56.1"
 
 [features]
 default = ["channel_reporter"]
-channel_reporter = ["crossbeam-channel", "once_cell"]
+channel_reporter = ["crossbeam-channel"]
 
 [dependencies.crossbeam-channel]
 version = "0.5"
 optional = true
 
-# Pin the once_cell version to 1.14, to keep the MSRV 1.38; once_cell 1.15 has an MSRV of 1.56.
-# once_cell itself is not directly used by storyteller, but we depend on it down-tree via crossbeam-channel.
-#
-# once_cell changelog: https://github.com/matklad/once_cell/blob/master/CHANGELOG.md#1150
-[dependencies.once_cell]
-version = "~1.14.0"
-optional = true
-
 [dev-dependencies]
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"