documentation: update CI config path

DEVELOPING.md

@@ -11,7 +11,7 @@ Ergo vendors all its dependencies. Because of this, Ergo is self-contained and y
 
 If you're upgrading the Go version used by Ergo, there are several places where it's hard-coded and must be changed:
 
-1. `.travis.yml`, which controls the version that our CI test suite uses to build and test the code (e.g., for a PR)
+1. `.github/workflows/build.yml`, which controls the version that our CI test suite uses to build and test the code (e.g., for a PR)
 2. `Dockerfile`, which controls the version that the Ergo binaries in our Docker images are built with
 3. `go.mod`: this should be updated automatically by Go when you do module-related operations