[IMP] readme: use https urls

For status images

closes odoo/odoo#78666

Signed-off-by: Martin Trigaux (mat) <mat@odoo.com>

README.md

-[![Build Status](http://runbot.odoo.com/runbot/badge/flat/1/master.svg)](http://runbot.odoo.com/runbot)
-[![Tech Doc](http://img.shields.io/badge/master-docs-875A7B.svg?style=flat&colorA=8F8F8F)](http://www.odoo.com/documentation/master)
-[![Help](http://img.shields.io/badge/master-help-875A7B.svg?style=flat&colorA=8F8F8F)](https://www.odoo.com/forum/help-1)
-[![Nightly Builds](http://img.shields.io/badge/master-nightly-875A7B.svg?style=flat&colorA=8F8F8F)](http://nightly.odoo.com/)
+[![Build Status](https://runbot.odoo.com/runbot/badge/flat/1/master.svg)](https://runbot.odoo.com/runbot)
+[![Tech Doc](https://img.shields.io/badge/master-docs-875A7B.svg?style=flat&colorA=8F8F8F)](https://www.odoo.com/documentation/master)
+[![Help](https://img.shields.io/badge/master-help-875A7B.svg?style=flat&colorA=8F8F8F)](https://www.odoo.com/forum/help-1)
+[![Nightly Builds](https://img.shields.io/badge/master-nightly-875A7B.svg?style=flat&colorA=8F8F8F)](https://nightly.odoo.com/)
 
 Odoo
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