CI Allow Rust lint unexpected_cfgs for cfg CHANNEL_NIGHTLY

Author: SpriteOvO

.github/workflows/ci.yml

@@ -125,9 +125,9 @@ jobs:
     - name: Run rustdoc
       run: |
         cd spdlog
-        cargo +nightly rustdoc --all-features --verbose -- -D warnings
+        cargo +nightly rustdoc --all-features --verbose -- -D warnings -A unexpected_cfgs
         cd ../spdlog-macros
-        cargo +nightly rustdoc --all-features --verbose -- -D warnings
+        cargo +nightly rustdoc --all-features --verbose -- -D warnings -A unexpected_cfgs
 
   check-msrv:
     strategy: