Modify default features in Cargo.toml

Updated the default features to the original values

Author: karandeol-26

Cargo.toml

@@ -86,7 +86,7 @@ bls12_381 = {git = "https://github.com/woopuiyung/bls12_381.git", branch = "rele
 approx = "0.5.0"
 
 [features]
-default = []
+default = ["bellman", "r1cs", "poly", "smt", "zok", "datalog", "multicore", "spartan"]
 # frontends
 c = ["lang-c"]
 zok = ["smt", "zokrates_parser", "zokrates_pest_ast", "typed-arena", "petgraph"]