Enforce rubocop layout rules

[Splines]

The only thing I've done here, is to run the following command inside the app folder (with rubocop version 1.50.2).

rubocop --config ../.rubocop.yml --fix-layout

See the docs for this command. There are no logical changes, just pure layout stuff. E.g. consistent line indentation, a newline at the end of every file. Also note that this does not affect .erb files at all.

⚠ Squash #494 beforehand.

[codecov]

Codecov Report

Merging #495 (2de4b26) into mampf-next (b119ec9) will decrease coverage by 0.08%.
The diff coverage is 46.93%.

@@              Coverage Diff               @@
##           mampf-next     #495      +/-   ##
==============================================
- Coverage       66.64%   66.56%   -0.08%     
==============================================
  Files             311      311              
  Lines            9362     9376      +14     
==============================================
+ Hits             6239     6241       +2     
- Misses           3123     3135      +12     

Impacted Files	Coverage Δ
app/abilities/medium_ability.rb	60.86% <0.00%> (ø)
app/helpers/announcements_helper.rb	36.36% <ø> (ø)
app/helpers/application_helper.rb	38.57% <0.00%> (ø)
app/helpers/assignments_helper.rb	36.36% <ø> (ø)
app/helpers/chapters_helper.rb	66.66% <ø> (ø)
app/helpers/clickers_helper.rb	22.22% <ø> (ø)
app/helpers/courses_helper.rb	43.75% <ø> (ø)
app/helpers/items_helper.rb	45.45% <ø> (ø)
app/helpers/lectures_helper.rb	35.18% <0.00%> (ø)
app/helpers/lessons_helper.rb	42.85% <ø> (ø)
... and 79 more