[stable-3.10] Bugfix/remove dead oauth code

[claucambra]

No description provided.

[nextcloud-desktop-bot]

AppImage file: nextcloud-PR-6075-498316c2af4b04b99f0eb386979f346c623520af-x86_64.AppImage

To test this change/fix you can simply download above AppImage file and test it.

Please make sure to quit your existing Nextcloud app and backup your data.

[codecov]

Codecov Report

Merging #6075 (498316c) into stable-3.10 (d299e57) will decrease coverage by 0.10%.
Report is 8 commits behind head on stable-3.10.
The diff coverage is 27.27%.

Additional details and impacted files

@@               Coverage Diff               @@
##           stable-3.10    #6075      +/-   ##
===============================================
- Coverage        60.42%   60.33%   -0.10%     
===============================================
  Files              145      145              
  Lines            18868    18793      -75     
===============================================
- Hits             11401    11338      -63     
+ Misses            7467     7455      -12     

Files Changed	Coverage Δ
src/libsync/creds/httpcredentials.h	25.00% <ø> (+5.00%)	⬆️
src/libsync/networkjobs.cpp	54.63% <0.00%> (-4.67%)	⬇️
src/libsync/networkjobs.h	4.16% <ø> (-8.34%)	⬇️
src/libsync/propagatedownload.cpp	66.85% <ø> (ø)
src/libsync/theme.cpp	19.35% <ø> (-0.35%)	⬇️
src/libsync/theme.h	60.00% <ø> (ø)
src/libsync/creds/httpcredentials.cpp	20.14% <42.85%> (+2.89%)	⬆️

... and 4 files with indirect coverage changes

[sonarcloud]

SonarCloud Quality Gate failed.   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

14.3% Coverage
0.0% Duplication

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