GH-46794: [CI][Dev] fix shellcheck errors in the ci/scripts/csharp_test.sh

Author: hiroyuki-sato

.pre-commit-config.yaml

@@ -305,6 +305,7 @@ repos:
           ?^ci/scripts/cpp_test\.sh$|
           ?^ci/scripts/csharp_build\.sh$|
           ?^ci/scripts/csharp_pack\.sh$|
+          ?^ci/scripts/csharp_test\.sh$|
           ?^ci/scripts/download_tz_database\.sh$|
           ?^ci/scripts/install_azurite\.sh$|
           ?^ci/scripts/install_ccache\.sh$|