Add nginx 1.17.8, remove nginx 1.17.7
Add nginx 1.17.8, remove nginx 1.17.7

for stack(s) cflinuxfs3 [#170822217]

cloudfoundry/php-buildpack,cloudfoundry/php-buildpack,cloudfoundry/php-buildpack,cloudfoundry/php-buildpack,cloudfoundry/php-buildpack,cloudfoundry/php-buildpack,cloudfoundry/php-buildpack