ci: relax errors on warnings

Fishrock123 · Fishrock123 · commit e62f1efe6075 · 2021-03-06T18:32:09.000-08:00
missing_doc_code_examples was renamed to rustdoc::missing_doc_code_examples on nightly but the rustdoc lint tool namespace doesn't exist on stable.
diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
@@ -7,9 +7,6 @@ on:
       - staging
       - trying
 
-env:
-  RUSTFLAGS: -Dwarnings
-
 jobs:
   build_and_test:
     name: Build and test
