Bump MSRV in CI

Author: newpavlov

.github/workflows/test.yml

@@ -43,7 +43,7 @@ jobs:
             # Test both windows-gnu and windows-msvc; use beta rust on one
           - os: ubuntu-latest
             target: x86_64-unknown-linux-gnu
-            toolchain: 1.51.0 # MSRV
+            toolchain: 1.56.0 # MSRV
           - os: ubuntu-latest
             deps: sudo apt-get update ; sudo apt install gcc-multilib
             target: i686-unknown-linux-gnu

rand_chacha/src/chacha.rs

@@ -634,6 +634,7 @@ mod test {
     }
 
     #[test]
+    #[cfg(feature = "std")]
     fn test_trait_objects() {
         use rand_core::CryptoRng;