Remove the fallback on clang-{tidy,format}

[lbonn]

This creates more problems than it solves.

We've talked about it, here it is.

We can also think about switching to newer versions later, but it would probably need some effort to make the lint happy.

[pattivacek]

Yeah, it's time and this seems like the right thing to do for now.

[codecov-io]

Codecov Report

Merging #1240 into master will increase coverage by 0.15%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1240      +/-   ##
==========================================
+ Coverage   79.31%   79.47%   +0.15%     
==========================================
  Files         170      170              
  Lines       10123    10123              
==========================================
+ Hits         8029     8045      +16     
+ Misses       2094     2078      -16

Impacted Files	Coverage Δ
src/libaktualizr/storage/sqlstorage_base.cc	76.35% <0%> (-2.03%)	⬇️
src/libaktualizr/storage/sqlstorage.cc	76.57% <0%> (+0.51%)	⬆️
src/libaktualizr/uptane/imagesrepository.cc	93.2% <0%> (+0.61%)	⬆️
src/libaktualizr/primary/sotauptaneclient.cc	93.07% <0%> (+0.75%)	⬆️
src/aktualizr_primary/secondary.cc	87.67% <0%> (+1.36%)	⬆️
src/libaktualizr/uptane/directorrepository.cc	97.14% <0%> (+1.42%)	⬆️
src/libaktualizr/package_manager/ostreemanager.cc	77.11% <0%> (+1.69%)	⬆️
src/libaktualizr-posix/ipuptanesecondary.cc	86.66% <0%> (+4%)	⬆️

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