fix: school.country is optional

[SKairinos]

This change is 

[faucomte97]

Reviewed 5 of 5 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @SKairinos)

---

portal/forms/organisation.py line 21 at r1 (raw file):

        help_texts = {
            "name": "Name of school or club",
            "postcode": "Postcode / Zipcode",

Just making a not here that it's weird that the postcode isn't optional when the country is, but since it's part of the second task we'll just need to make sure we don't deploy this yet until it's done.

[codecov]

Codecov Report

Merging #2228 (3856453) into master (b8dc731) will decrease coverage by 0.15%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2228      +/-   ##
==========================================
- Coverage   94.27%   94.12%   -0.15%     
==========================================
  Files         168      169       +1     
  Lines        4594     4599       +5     
==========================================
- Hits         4331     4329       -2     
- Misses        263      270       +7     

Files	Coverage Δ
...mon/common/migrations/0046_alter_school_country.py	100.00% <100.00%> (ø)
cfl_common/common/models.py	89.91% <100.00%> (ø)
portal/forms/organisation.py	100.00% <100.00%> (ø)
portal/views/organisation.py	98.24% <100.00%> (ø)
portal/views/teacher/dashboard.py	95.23% <100.00%> (-1.79%)	⬇️

... and 1 file with indirect coverage changes