test-renderers: Clean up port feature dependencies.

`all-is-cubes-port` is used only by the glTF test, so the `gltf`
feature should enable it and there's no need for enabling specific
features.

This is a workaround for <rust-lang/cargo#14016>
affecting my testing against nightly & edition 2024. I'm not sure
whether I prefer it overall.

Author: kpreid

test-renderers/Cargo.toml

@@ -51,8 +51,7 @@ auto-threads = [
     "all-is-cubes-render/auto-threads",
 ]
 gltf = [
-    "all-is-cubes-port/export",
-    "all-is-cubes-port/gltf",
+    "dep:all-is-cubes-port",
     "dep:rend3",
     "dep:rend3-gltf",
     "dep:rend3-routine",
@@ -65,7 +64,8 @@ gltf = [
 all-is-cubes = { workspace = true, features = ["save"] }
 all-is-cubes-content = { workspace = true }
 all-is-cubes-gpu = { workspace = true, features = ["wgpu"] }
-all-is-cubes-port = { workspace = true, optional = true }
+# used only for gltf export+render tests
+all-is-cubes-port = { workspace = true, optional = true, features = ["export", "gltf"] }
 all-is-cubes-render = { workspace = true, features = ["raytracer", "std"] }
 all-is-cubes-ui = { workspace = true }
 async_fn_traits = { workspace = true }