[stable13] Fix user selectable text for public links for text files

[MorrisJobke]

Backport of #9206

[codecov]

Codecov Report

Merging #9230 into stable13 will increase coverage by <.01%.
The diff coverage is n/a.

@@              Coverage Diff               @@
##             stable13    #9230      +/-   ##
==============================================
+ Coverage       51.33%   51.34%   +<.01%     
  Complexity      25040    25040              
==============================================
  Files            1609     1609              
  Lines           95317    95317              
  Branches         1376     1376              
==============================================
+ Hits            48929    48936       +7     
+ Misses          46388    46381       -7

Impacted Files	Coverage Δ	Complexity Δ
apps/files_trashbin/lib/Trashbin.php	72.53% <0%> (+0.24%)	136% <0%> (ø)	⬇️
core/js/js.js	66.29% <0%> (+0.55%)	0% <0%> (ø)	⬇️
apps/files_trashbin/lib/Expiration.php	91.93% <0%> (+1.61%)	29% <0%> (ø)	⬇️

[danxuliu]

Tested and works 👍

Note that in stable13 the Text editor app is not used for text previews (although that would change if nextcloud/files_texteditor#71 was backported), so in this branch this change (currently) affects only the default text preview.