cargo: Remove gtk-macros dependency

Using the crate is depreacted. Replaced spawn! macro
with our own spawn function

Cargo.lock

@@ -1439,12 +1439,6 @@ dependencies = [
  "system-deps",
 ]
 
-[[package]]
-name = "gtk-macros"
-version = "0.3.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "da5bf7748fd4cd0b2490df8debcc911809dbcbee4ece9531b96c29a9c729de5a"
-
 [[package]]
 name = "gtk4"
 version = "0.6.4"
@@ -1903,7 +1897,6 @@ dependencies = [
  "futures",
  "gettext-rs",
  "gio",
- "gtk-macros",
  "gtk4",
  "image",
  "indexmap",