l10n: Change "at" to "on"

[Valdnet]

Reported by a Transifex translator.

[codecov]

Codecov Report

Merging #3140 (fcc43b2) into master (e69a53a) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #3140   +/-   ##
=========================================
  Coverage     28.92%   28.92%           
  Complexity      121      121           
=========================================
  Files           157      157           
  Lines          5715     5715           
  Branches        839      839           
=========================================
  Hits           1653     1653           
  Misses         4062     4062           

Flag	Coverage Δ
javascript	23.45% <ø> (ø)
php	94.54% <ø> (ø)

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Impacted Files	Coverage Δ
...components/AppNavigation/CalendarList/Trashbin.vue	0.00% <ø> (ø)

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[ChristophWurst]

It's the column header for a relative date. This will now say Deleted on … 2 days ago. This doesn't seem right. Should it be just Deleted maybe?

[Valdnet]

Should it be just Deleted maybe?

A very good solution. I thought so too (because it's in the table), but I wanted your opinion.

Corrected 😉. @ChristophWurst I am asking you to merge.