Move .codecov.yml

>  the file must still be located in the root, dev/, or .github/ directories

https://docs.codecov.io/docs/codecov-yaml#can-i-name-the-file-codecovyml

.github/codecov.yml

@@ -0,0 +1,8 @@
+fixes:
+  - "::Library/Homebrew/"
+coverage:
+  round: nearest
+  status:
+    project:
+      default:
+        threshold: 0.05%

Library/Homebrew/test/.codecov.yml

@@ -1,9 +0,0 @@
-codecov:
-  fixes:
-   - "::Library/Homebrew/"
-  coverage:
-    round: nearest
-    status:
-      project:
-        default:
-          threshold: 0.05%