refactor: move declaration of remote user out of inventory file

This change reduces differences between prod.inventory and mystamps.inventory to let us merge them
later.

Part of #1631

[skip ci]

Author: php-coder

infra/vagrant/provisioning/prod.inventory

@@ -5,7 +5,6 @@
 my-stamps.ru ansible_host=46.101.232.167
 
 [all:vars]
-ansible_user=coder
 ansible_ssh_private_key_file=/Users/coder/.ssh/mystamps_rsa
 
 # https://docs.ansible.com/ansible/2.10/reference_appendices/python_3_support.html#using-python-3-on-the-managed-machines-with-commands-and-playbooks

infra/vagrant/provisioning/prod.yml

@@ -1,6 +1,7 @@
 ---
 - hosts: all
   gather_facts: no
+  remote_user: coder
   become: yes
   become_method: sudo
   vars: