bump minimum Rust to 1.59

27c5ed5 uses destructuring assignments, introduced in this version.
Should address this CI failure:
https://github.com/scottlamb/retina/actions/runs/2303800235

.github/workflows/ci.yml

@@ -12,7 +12,7 @@ jobs:
       matrix:
         rust:
           - stable
-          - 1.56
+          - 1.59
         include:
           - rust: stable
             extra_components: rustfmt

Cargo.toml

@@ -9,7 +9,7 @@ categories = ["network-programming", "multimedia"]
 description = "high-level RTSP multimedia streaming library"
 repository = "https://github.com/scottlamb/retina"
 include = ["src/**/*", "benches", "Cargo.toml"]
-rust-version = "1.56"
+rust-version = "1.59"
 
 [dependencies]
 base64 = "0.13.0"