chore: update png dependency version to 0.18 (#295)

Author: thief-sty

.changes/update-png-to-0-18.md

@@ -0,0 +1,7 @@
+---
+"tray-icon": patch
+---
+
+Update png dependency version to 0.18.
+
+This avoids duplicated dependencies in downstream crates.

.changes/update-rust-to-1-73.md

@@ -0,0 +1,5 @@
+---
+"tray-icon": minor
+---
+
+Update rust version to 1.73.

.github/workflows/test.yml

@@ -35,7 +35,7 @@ jobs:
           sudo apt-get update
           sudo apt-get install -y libgtk-3-dev libxdo-dev libayatana-appindicator3-dev
 
-      - uses: dtolnay/rust-toolchain@1.71
+      - uses: dtolnay/rust-toolchain@1.73
       - run: cargo build
 
       - uses: dtolnay/rust-toolchain@stable

Cargo.lock

@@ -7,7 +7,7 @@ homepage = "https://github.com/tauri-apps/tray-icon"
 repository = "https://github.com/tauri-apps/tray-icon"
 license = "MIT OR Apache-2.0"
 categories = ["gui"]
-rust-version = "1.71"
+rust-version = "1.73"
 include = ["README.md", "src/**/*.rs", "Cargo.toml", "LICENSE-APACHE", "LICENSE-MIT", "LICENSE.spdx"]
 
 [features]
@@ -81,7 +81,7 @@ objc2-app-kit = { version = "0.3", default-features = false, features = [
 ] }
 
 [target."cfg(any(target_os = \"linux\", target_os = \"macos\"))".dependencies]
-png = "0.17"
+png = "0.18"
 
 [dev-dependencies]
 winit = "0.30"