build: bump once_cell from 1.13.1 to 1.14.0

Bumps [once_cell](https://github.com/matklad/once_cell) from 1.13.1 to 1.14.0.
- [Release notes](https://github.com/matklad/once_cell/releases)
- [Changelog](https://github.com/matklad/once_cell/blob/master/CHANGELOG.md)
- [Commits](https://github.com/matklad/once_cell/compare/v1.13.1...v1.14.0)

---
updated-dependencies:
- dependency-name: once_cell
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

vmm/Cargo.toml

@@ -34,7 +34,7 @@ linux-loader = { version = "0.4.0", features = ["elf", "bzimage", "pe"] }
 log = "0.4.17"
 micro_http = { git = "https://github.com/firecracker-microvm/micro-http", branch = "main" }
 net_util = { path = "../net_util" }
-once_cell = "1.13.1"
+once_cell = "1.14.0"
 option_parser = { path = "../option_parser" }
 pci = { path = "../pci" }
 qcow = { path = "../qcow" }