Remove paths from dependencies

Now that we have extracted the release changes from the
zcash/librustzcash subtree, we are no longer in a workspace with
relative paths to these dependencies.

Cargo.toml

@@ -12,19 +12,19 @@ edition = "2018"
 [dependencies]
 bit-vec = "0.6"
 blake2s_simd = "0.5"
-ff = { version = "0.7", path = "../ff" }
+ff = "0.7"
 futures = "0.1"
 futures-cpupool = { version = "0.1", optional = true }
-group = { version = "0.7", path = "../group" }
+group = "0.7"
 num_cpus = { version = "1", optional = true }
 crossbeam = { version = "0.7", optional = true }
-pairing = { version = "0.17", path = "../pairing", optional = true }
+pairing = { version = "0.17", optional = true }
 rand_core = "0.5"
 byteorder = "1"
 subtle = "2.2.1"
 
 [dev-dependencies]
-bls12_381 = { version = "0.2", path = "../bls12_381" }
+bls12_381 = "0.2"
 hex-literal = "0.2"
 rand = "0.7"
 rand_xorshift = "0.2"