Switch target to 64bit and enable the zbb feature (#120)

crates/runtime-api/Cargo.toml

@@ -7,9 +7,6 @@ repository.workspace = true
 authors.workspace = true
 description = "Implements the low level runtime API bindings with pallet contracts"
 
-[features]
-riscv-64 = []
-
 [dependencies]
 anyhow = { workspace = true }
 inkwell = { workspace = true, features = ["target-riscv", "no-libffi-linking", "llvm18-0"] }