Bump the gtk group across 1 directory with 3 updates

Updates the requirements on [glib](https://github.com/gtk-rs/gtk-rs-core), [glib-sys](https://github.com/gtk-rs/gtk-rs-core) and [gio](https://github.com/gtk-rs/gtk-rs-core) to permit the latest version.

Updates `glib` to 0.18.5
- [Release notes](https://github.com/gtk-rs/gtk-rs-core/releases)
- [Changelog](https://github.com/gtk-rs/gtk-rs-core/blob/master/CHANGELOG.md)
- [Commits](gtk-rs/gtk-rs-core@0.18.0...0.18.5)

Updates `glib-sys` to 0.20.2
- [Release notes](https://github.com/gtk-rs/gtk-rs-core/releases)
- [Changelog](https://github.com/gtk-rs/gtk-rs-core/blob/master/CHANGELOG.md)
- [Commits](gtk-rs/gtk-rs-core@0.18.0...0.20.2)

Updates `gio` to 0.18.4
- [Release notes](https://github.com/gtk-rs/gtk-rs-core/releases)
- [Changelog](https://github.com/gtk-rs/gtk-rs-core/blob/master/CHANGELOG.md)
- [Commits](gtk-rs/gtk-rs-core@0.18.0...0.18.4)

---
updated-dependencies:
- dependency-name: glib
  dependency-type: direct:production
  dependency-group: gtk
- dependency-name: glib-sys
  dependency-type: direct:production
  dependency-group: gtk
- dependency-name: gio
  dependency-type: direct:production
  dependency-group: gtk
...

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

Cargo.toml

@@ -13,13 +13,13 @@ license = "MIT"
 system-deps = "7"
 libc = "0.2"
 bitflags = "2"
-glib = "0.18"
-glib-sys = "0.18"
+glib = "0.20"
+glib-sys = "0.20"
 gdk = { version = "0.18", features = ["v3_24"] }
 gdk-sys = "0.18"
 gtk-sys = "0.18"
 gtk = "0.18"
-gio = "0.18"
+gio = "0.20"
 shell-words = "1.0"
 tempfile = "3"
 gtk-layer-shell-sys = { path = "gtk-layer-shell-sys", version = "0.7" }