chore(deps): bump once_cell from 1.14.0 to 1.15.0

Bumps [once_cell](https://github.com/matklad/once_cell) from 1.14.0 to 1.15.0.
- [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/v1.14.0...v1.15.0)

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

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

Cargo.lock

@@ -285,9 +285,9 @@ dependencies = [
 
 [[package]]
 name = "once_cell"
-version = "1.14.0"
+version = "1.15.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2f7254b99e31cad77da24b08ebf628882739a608578bb1bcdfc1f9c21260d7c0"
+checksum = "e82dad04139b71a90c080c8463fe0dc7902db5192d939bd0950f074d014339e1"
 
 [[package]]
 name = "pem"

Cargo.toml

@@ -19,7 +19,7 @@ getopts = "0.2.21"
 glob = "0.3"
 log = "0.4"
 mime_guess = "2.0"
-once_cell = "1.14"
+once_cell = "1.15"
 percent-encoding = "2.2"
 rcgen = { version = "0.9.3" }
 rustls = "0.20.6"