Set -Dwarnings via CI env rather than cfg

Author: tgross35

.github/workflows/main.yaml

@@ -4,6 +4,10 @@ on: [push, pull_request]
 permissions:
   contents: read
 
+env:
+  RUSTDOCFLAGS: -Dwarnings
+  RUSTFLAGS: -Dwarnings
+
 jobs:
   test:
     name: Test

src/lib.rs

@@ -26,7 +26,6 @@
 #![no_std]
 #![doc(html_root_url = "https://docs.rs/cfg-if")]
 #![deny(missing_docs)]
-#![cfg_attr(test, deny(warnings))]
 #![cfg_attr(test, allow(unexpected_cfgs))] // we test with features that do not exist
 
 /// The main macro provided by this crate. See crate documentation for more