[#1808] Use long month name in maandspecificatie

[pi-sigma]

Taiga #1808

[codecov-commenter]

Codecov Report

Merging #812 (db94289) into develop (5a60c3e) will decrease coverage by 0.02%.
Report is 4 commits behind head on develop.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop     #812      +/-   ##
===========================================
- Coverage    93.05%   93.04%   -0.02%     
===========================================
  Files          742      742              
  Lines        25821    25825       +4     
===========================================
+ Hits         24028    24029       +1     
- Misses        1793     1796       +3     

Files	Coverage Δ
src/open_inwoner/ssd/forms.py	96.29% <100.00%> (ø)
src/open_inwoner/ssd/templatetags/ssd_tags.py	95.45% <100.00%> (ø)
src/open_inwoner/ssd/tests/test_forms.py	100.00% <100.00%> (ø)
src/open_inwoner/ssd/tests/test_xml.py	100.00% <ø> (ø)

... and 1 file with indirect coverage changes

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