Merge pull request #8225 from The-Compiler/training-update (#8226)

doc: Add note about training early bird discount

Author: nicoddemus

doc/en/index.rst

@@ -2,7 +2,7 @@
 
 .. sidebar:: Next Open Trainings
 
-   - `Professional testing with Python <https://www.python-academy.com/courses/specialtopics/python_course_testing.html>`_, via Python Academy, February 1-3 2021, Leipzig (Germany) and remote.
+   - `Professional testing with Python <https://www.python-academy.com/courses/specialtopics/python_course_testing.html>`_, via Python Academy, February 1-3 2021, remote and Leipzig (Germany). **Early-bird discount available until January 15th**.
 
    Also see `previous talks and blogposts <talks.html>`_.