Remove useless "set title"

[int-y1]

Remove uses of set title that break i18n. Affected pages:

/contests/
/organizations/
/problems/
/stats/language/
/users/

[codecov-commenter]

Codecov Report

Merging #1924 (c7f2b5c) into master (70cc14b) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1924   +/-   ##
=======================================
  Coverage   46.41%   46.41%           
=======================================
  Files         235      235           
  Lines       13107    13107           
=======================================
  Hits         6084     6084           
  Misses       7023     7023           

Impacted Files	Coverage Δ
judge/models/submission.py	90.50% <ø> (ø)
judge/views/stats.py	45.94% <ø> (ø)

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