chore(deps): bump google/cloud-sdk in /.dev/spanner

Bumps google/cloud-sdk from 518.0.0-emulators to 519.0.0-emulators.

---
updated-dependencies:
- dependency-name: google/cloud-sdk
  dependency-version: 519.0.0-emulators
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.dev/spanner/Dockerfile

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-FROM google/cloud-sdk:518.0.0-emulators
+FROM google/cloud-sdk:519.0.0-emulators
 # TARGETARCH is an automatic platform ARG enabled by Docker BuildKit.
 # https://docs.docker.com/reference/dockerfile/#automatic-platform-args-in-the-global-scope
 ARG TARGETARCH