Clean up apt lists after installation in Dockerfile

Dockerfile

@@ -9,7 +9,8 @@ RUN apt-get update && apt-get install -y \
     && docker-php-ext-install -j$(nproc) iconv \
     && docker-php-ext-configure gd --with-freetype=/usr/include/ --with-jpeg=/usr/include/ \
     && docker-php-ext-configure pgsql -with-pgsql=/usr/local/pgsql \
-    && docker-php-ext-install -j$(nproc) gd pdo pdo_mysql pdo_pgsql pgsql
+    && docker-php-ext-install -j$(nproc) gd pdo pdo_mysql pdo_pgsql pgsql \
+    && rm -rf /var/lib/apt/lists/*
 
 # Prepare files and folders