Update nginx Docker tag to v1.28.0

Author: renovate-bot

images/custom-nginx/Dockerfile

@@ -11,7 +11,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-FROM nginx:1.17.9-alpine
+FROM nginx:1.28.0-alpine
 
 COPY ./nginx.conf /etc/nginx/nginx.conf
 COPY ./default.conf /etc/nginx/conf.d/default.conf