[stable-3.9] add link in readme to nextcloud-releases correct page with binaries

[backportbot-nextcloud]

Backport of #5864

[codecov]

Codecov Report

Merging #5880 (d6bf368) into stable-3.9 (6843441) will decrease coverage by 0.01%.
The diff coverage is 77.77%.

❗ Current head d6bf368 differs from pull request most recent head 1c16374. Consider uploading reports for the commit 1c16374 to get more accurate results

Additional details and impacted files

@@              Coverage Diff               @@
##           stable-3.9    #5880      +/-   ##
==============================================
- Coverage       60.42%   60.41%   -0.01%     
==============================================
  Files             145      145              
  Lines           18609    18605       -4     
==============================================
- Hits            11245    11241       -4     
  Misses           7364     7364              

Impacted Files	Coverage Δ
src/libsync/putmultifilejob.cpp	88.46% <50.00%> (-3.38%)	⬇️
src/common/checksumcalculator.cpp	86.58% <100.00%> (-1.06%)	⬇️

... and 2 files with indirect coverage changes

[nextcloud-desktop-bot]

AppImage file: nextcloud-PR-5880-1c1637406479e052a464da871511c1c79635cd3e-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.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

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No Coverage information
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