remove: parallel feature and use it in deps

After reading about `rayon` fallback in non-threaded targets. See:
https://docs.rs/rayon-core/1.12.1/rayon_core/index.html#global-fallback-when-threading-is-unsupported
the decision has been to actually use `parallel` feature for all
dependencies that have it always.

Cargo.toml

@@ -18,12 +18,12 @@ num-bigint = { version = "=0.4.3", default-features = false, features = ["rand"]
 
 # ZKP Generation
 ark-crypto-primitives = { version = "=0.4.0" }
-ark-ec = { version = "=0.4.1", default-features = false }
-ark-ff = { version = "=0.4.1", default-features = false, features = ["parallel", "asm"] }
-ark-std = { version = "=0.4.0", default-features = false }
+ark-ec = { version = "=0.4.1", default-features = false, features = ["parallel"] }
+ark-ff = { version = "=0.4.1", default-features = false, features = ["asm", "parallel"] }
+ark-std = { version = "=0.4.0", default-features = false, features = ["parallel"] }
 ark-bn254 = { version = "=0.4.0" }
-ark-groth16 = { version = "=0.4.0", default-features = false }
-ark-poly = { version = "=0.4.1", default-features = false }
+ark-groth16 = { version = "=0.4.0", default-features = false, features = ["parallel"] }
+ark-poly = { version = "=0.4.1", default-features = false, features = ["parallel"] }
 ark-relations = { version = "=0.4.0", default-features = false }
 ark-serialize = { version = "=0.4.1", default-features = false }
 
@@ -51,9 +51,9 @@ ethers = "=2.0.7"
 name = "groth16"
 harness = false
 
+
 [features]
-default = ["parallel", "wasmer/default", "circom-2", "ethereum"]
-parallel = ["ark-ec/parallel", "ark-ff/parallel", "ark-std/parallel",  "ark-groth16/parallel", "ark-poly/parallel"]
+default = ["wasmer/default", "circom-2", "ethereum"]
 wasm = ["wasmer/js-default"]
 bench-complex-all = []
 circom-2 = []