[#1144] Fix/update birthday date format in mydata

[vaszig]

No description provided.

[codecov-commenter]

Codecov Report

Merging #476 (9745370) into develop (6107ac5) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop     #476   +/-   ##
========================================
  Coverage    96.46%   96.46%           
========================================
  Files          506      506           
  Lines        18263    18300   +37     
========================================
+ Hits         17617    17654   +37     
  Misses         646      646           

Impacted Files	Coverage Δ
src/open_inwoner/openzaak/documents.py	94.59% <ø> (ø)
.../open_inwoner/accounts/tests/test_profile_views.py	100.00% <100.00%> (ø)
src/open_inwoner/accounts/views/profile.py	99.16% <100.00%> (+0.03%)	⬆️
src/open_inwoner/haalcentraal/tests/test_signal.py	100.00% <100.00%> (ø)
src/open_inwoner/haalcentraal/utils.py	91.04% <100.00%> (+1.04%)	⬆️
src/open_inwoner/accounts/forms.py	97.78% <0.00%> (ø)
src/open_inwoner/openzaak/models.py	97.82% <0.00%> (ø)
src/open_inwoner/accounts/views/cases.py	97.52% <0.00%> (ø)
...rc/open_inwoner/openzaak/tests/test_case_detail.py	100.00% <0.00%> (ø)

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[Bartvaderkin]

Technically it'd be better to parse the API data to Python data (eg: a Date), and then format that using Django's standard date localization.