Make our futures-rs fork a direct dependency again

Crates with patch sections can't be published on crates.io, so there is no advantage over a normal git dependency.

This reverts commit c862e66.

Author: phil-opp

Cargo.toml

@@ -43,15 +43,12 @@ default-features = false
 features = ["unicode"]
 
 [dependencies.futures-preview]
-version = "0.3.0-alpha"
+git = "https://github.com/embed-rs/futures-rs.git"
+branch = "alloc"
 default-features = false
 features = ["alloc"]
 
 [profile.release]
 codegen-units = 1 # better optimizations
 debug = true
 lto = true # better optimizations
-
-[patch.crates-io.futures-preview]
-git = "https://github.com/embed-rs/futures-rs.git"
-branch = "alloc"