Pin requests to version 2.31.0 in main.yml (#12959)

What is the motivation for this PR?
In latest requests python package, would got error in some steps like add-topo and restart-ptf with message 'Not supported URL scheme http+docker'
We already have fix PR #12910 in master branch to install stable requests version in docker.yml, but once package_installation was set to false like restart-ptf, docker.yml would skip and report error again

How did you do it?
Install stable requests version in main.yml after executing docker.yml to cover all scenario

Author: xwjiang-ms

ansible/roles/vm_set/tasks/main.yml

@@ -124,6 +124,21 @@
 - include_tasks: docker.yml
   when: package_installation|bool
 
+- name: Update python3 packages
+  block:
+    # Workaround for '"Error connecting: Error while fetching server API version: Not supported URL scheme http+docker'
+    # See https://github.com/docker/docker-py/issues/3256
+  - name: Remove old requests package >=2.32.0
+    pip: name=requests state=absent executable={{ pip_executable }}
+    become: yes
+    environment: "{{ proxy_env | default({}) }}"
+    ignore_errors: yes
+  - name: Install requests package <2.32.0
+    pip: name=requests version=2.31.0 state=present executable={{ pip_executable }}
+    become: yes
+    environment: "{{ proxy_env | default({}) }}"
+  when: pip_executable=="pip3"
+
 - name: Ensure {{ ansible_user }} in docker,sudo group
   user:
     name: "{{ ansible_user }}"