Improve "from" time label in /tests/overview

[okurz]

The previous wording for example "from 2 days ago" could be understood
as showing jobs starting 2 days ago until now. This commit changes the
wording to make it clear that we mean jobs until that specified
timestamp. So in the above example the text would say "at the time of 2
days ago".

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.04%. Comparing base (0a4478b) to head (90636cd).
Report is 4 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #6300   +/-   ##
=======================================
  Coverage   99.04%   99.04%           
=======================================
  Files         398      398           
  Lines       40034    40034           
=======================================
  Hits        39650    39650           
  Misses        384      384           

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