feat(deps): Update php to version 7.4 (#5724)

Dockerfile

@@ -106,7 +106,10 @@ ENV PATH $PATH:/opt/elixir-${ELIXIR_VERSION}/bin
 
 # PHP Composer
 
-RUN apt-get update && apt-get install -y php-cli php-mbstring && \
+RUN echo "deb http://ppa.launchpad.net/ondrej/php/ubuntu bionic main" > /etc/apt/sources.list.d/ondrej-php.list && \
+    apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 14AA40EC0831756756D7F66C4F4EA0AAE5267A6C && \
+    apt-get update && \
+    apt-get -y install php7.4-cli php7.4-mbstring && \
     rm -rf /var/lib/apt/lists/*
 
 ENV COMPOSER_VERSION=1.9.3