fix: TheIdServer.IS4/src/TIS.BlazorApp/Dockerfile to reduce vulnerabi…

…lities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-DEBIAN11-GZIP-2444256
- https://snyk.io/vuln/SNYK-DEBIAN11-PCRE2-2808697
- https://snyk.io/vuln/SNYK-DEBIAN11-PCRE2-2808704
- https://snyk.io/vuln/SNYK-DEBIAN11-TIFF-2774162
- https://snyk.io/vuln/SNYK-DEBIAN11-TIFF-2774167

TheIdServer.IS4/src/TIS.BlazorApp/Dockerfile

@@ -11,7 +11,7 @@ RUN dotnet build "TIS.BlazorApp.csproj" -c Release -o /app/build
 FROM build AS publish
 RUN dotnet publish "TIS.BlazorApp.csproj" -c Release -o /app/publish
 
-FROM nginx:latest AS final
+FROM nginx:1.21 AS final
 WORKDIR /usr/share/nginx/html
 COPY --from=publish /app/publish/wwwroot .
 COPY --from=build /src/src/TIS.BlazorApp/nginx.conf /etc/nginx/nginx.conf