Add nginx 1.15.12, remove nginx 1.15.11
Add nginx 1.15.12, remove nginx 1.15.11

for stack(s) cflinuxfs2, cflinuxfs3 [#165387664]

cf-identity/php-buildpack,cf-identity/php-buildpack,cf-identity/php-buildpack,cloudfoundry/php-buildpack,cloudfoundry/php-buildpack,cloudfoundry/php-buildpack,cf-identity/php-buildpack,cloudfoundry/php-buildpack,cf-identity/php-buildpack,cloudfoundry/php-buildpack,cloudfoundry/php-buildpack,cf-identity/php-buildpack,cf-identity/php-buildpack,cloudfoundry/php-buildpack