Update rustls-pemfile requirement from 1.0.0 to 2.1.1

Updates the requirements on [rustls-pemfile](https://github.com/rustls/pemfile) to permit the latest version.
- [Release notes](https://github.com/rustls/pemfile/releases)
- [Commits](rustls/pemfile@v/1.0.0...v/2.1.1)

---
updated-dependencies:
- dependency-name: rustls-pemfile
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

server/Cargo.toml

@@ -28,5 +28,5 @@ nalgebra = { workspace = true }
 libm = "0.2.6"
 slotmap = "1.0.6"
 rustls = "0.21.7"
-rustls-pemfile = "1.0.0"
+rustls-pemfile = "2.1.1"
 save = { path = "../save" }