Bump num-modular to v0.6 (#522)

Author: tarcieri

Cargo.lock

@@ -34,7 +34,7 @@ criterion = { version = "0.5", features = ["html_reports"] }
 hex-literal = "0.4"
 num-bigint = "0.4"
 num-integer = "0.1"
-num-modular = { version = "0.5", features = ["num-bigint"] }
+num-modular = { version = "0.6", features = ["num-bigint", "num-integer", "num-traits"] }
 proptest = "1"
 rand_core = { version = "0.6", features = ["std"] }
 rand_chacha = "0.3"