Downgrade once_cell from v1.15.0 to v1.14.0 to try to overcome the ms…

…rv failure.

Workflow log:

Downloaded once_cell v1.15.0
error: failed to parse manifest at `/home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/once_cell-1.15.0/Cargo.toml`
Error: failed to parse manifest at `/home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/once_cell-1.15.0/Cargo.toml`
Caused by:
  failed to parse the `edition` key

Caused by:
  this version of Cargo is older than the `2021` edition, and only supports `2015` and `2018` editions.
Error: The process '/home/runner/.cargo/bin/cargo' failed with exit code 101

Cargo.toml

@@ -19,6 +19,10 @@ hyper = "0.14.19"
 futures-channel = "0.3"
 futures-util = { version = "0.3", default-features = false }
 http = "0.2"
+
+# Necessary to overcome msrv check of rust 1.49, as 1.15.0 failed
+once_cell = "=1.14"
+
 pin-project-lite = "0.2.4"
 socket2 = "0.4"
 tracing = { version = "0.1", default-features = false, features = ["std"] }