added missing php line

Dockerfile

@@ -10,6 +10,7 @@ RUN git clone https://gerrit.wikimedia.org/r/mediawiki/extensions/MobileFrontend
     git clone https://gerrit.wikimedia.org/r/mediawiki/extensions/OpenIDConnect --branch REL1_40; \
     php -r "copy('https://getcomposer.org/installer', 'composer-setup.php');"; \
     php -r "if (hash_file('sha384', 'composer-setup.php') === 'e21205b207c3ff031906575712edab6f13eb0b361f2085f1f1237b7126d785e826a450292b6cfd1d64d92e6563bbde02') { echo 'Installer verified'; } else { echo 'Installer corrupt'; unlink('composer-setup.php'); } echo PHP_EOL;"; \
+    php composer-setup.php; \
     mv composer.phar /usr/local/bin/composer; \
     cd /var/www/html; \
     composer update --no-dev --optimize-autoloader; \