chore(deps): update nginx docker tag to v1.17.9 (#480)

Co-authored-by: Renovate Bot <bot@renovateapp.com>

Author: renovate[bot]

Phonebook.Frontend/Dockerfile

@@ -21,7 +21,7 @@ RUN npm run build
 ### production ###
 ##################
 
-FROM nginx:1.17.6
+FROM nginx:1.17.9
 WORKDIR /etc/nginx
 
 ARG BASE_URL

demo/assets/Dockerfile

@@ -1,4 +1,4 @@
-FROM nginx:1.17.6-alpine
+FROM nginx:1.17.9-alpine
 WORKDIR /etc/nginx
 
 RUN rm -r ./*