Don't run BouncyCastle test; it runs into errors

* What went wrong:
Could not determine the dependencies of task ':extern:bouncycastle:test'.
> Task with path ':core:test' not found in project ':extern:bouncycastle'.

.github/workflows/Android-CI-Espresso.yml

@@ -32,7 +32,7 @@ jobs:
       - name: Build project
         run: ./gradlew assemble
       - name: Run tests
-        run: ./gradlew test
+        run: ./gradlew :OpenKeychain:test
       - name: Archive UnitTest report
         uses: actions/upload-artifact@v2
         if: failure()