Stop compiling Java in dependency update workflow

The dependency update workflow should only refresh dependencies and generated sources. Remove the Java compile validation step so compilation failures are handled by normal CI instead of blocking update PR creation.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: stephentoub

.github/workflows/update-copilot-dependency.yml

@@ -114,10 +114,6 @@ jobs:
         working-directory: ./java
         run: mvn generate-sources -Pcodegen
 
-      - name: Compile Java SDK (validate generated code)
-        working-directory: ./java
-        run: mvn compile -Pskip-test-harness
-
       - name: Create pull request
         env:
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}