Update OPTIMADE capitalisation

[ml-evs]

Closes #232.

This PR was generated with find . -type f | xargs sed -i 's/OPTiMaDe/OPTIMADE/g'

[codecov]

Codecov Report

Merging #233 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #233   +/-   ##
=======================================
  Coverage   87.57%   87.57%           
=======================================
  Files          43       43           
  Lines        1916     1916           
=======================================
  Hits         1678     1678           
  Misses        238      238

Flag	Coverage Δ
#unittests	87.57% <ø> (ø)	⬆️

Impacted Files	Coverage Δ
optimade/models/links.py	92.59% <ø> (ø)	⬆️
optimade/filtertransformers/mongo.py	95.65% <ø> (ø)	⬆️
optimade/models/baseinfo.py	94.73% <ø> (ø)	⬆️
optimade/models/structures.py	92.5% <ø> (ø)	⬆️
optimade/server/data/__init__.py	100% <ø> (ø)	⬆️
optimade/server/routers/landing.py	66.66% <ø> (ø)	⬆️
optimade/server/main_index.py	80.39% <ø> (ø)	⬆️
optimade/models/responses.py	97.5% <ø> (ø)	⬆️
optimade/validator/validator_model_patches.py	100% <ø> (ø)	⬆️
optimade/server/query_params.py	100% <ø> (ø)	⬆️
... and 9 more

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