Remove default features when fullstack is enabled and one platform is enabled in the default features (#3925)

* Don't enable default features when only either the server or client is enabled

packages/playwright-tests/default-features-disabled/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "dioxus-playwright-default-features-disabled-test"
+version = "0.1.0"
+edition = "2021"
+publish = false
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+dioxus = { workspace = true, features = ["fullstack"] }
+
+[features]
+# Web is a default feature, but it shouldn't actually be enabled in server builds
+default = ["web"]
+server = ["dioxus/server"]
+web = ["dioxus/web"]