Remove redundant build step from workflow

Eliminated the step that builds the example_app binary in the CI workflow. Building the binary was unnecessary as the workflow already covers dependency installation, code formatting check, and running tests. Simplifies the workflow and reduces build times.

.github/workflows/crystal.yml

@@ -61,8 +61,6 @@ jobs:
       - uses: actions/checkout@v2
       - name: Install dependencies
         run: shards install
-      - name: Build binary to test
-        run: shards build example_app
       - name: Check code styl2e
         run: crystal tool format --check
       - name: Run tests