Fix line break for MS teams webhook

[ivanvc]

Adds an extra line break to multi commit messages from MS teams webhook.

This is how it looks now:

Fixes #12255.

[codecov-io]

Codecov Report

Merging #13081 into master will decrease coverage by 0.00%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master   #13081      +/-   ##
==========================================
- Coverage   42.60%   42.60%   -0.01%     
==========================================
  Files         673      673              
  Lines       73858    73858              
==========================================
- Hits        31466    31465       -1     
+ Misses      37292    37287       -5     
- Partials     5100     5106       +6     

Impacted Files	Coverage Δ
modules/webhook/msteams.go	0.00% <0.00%> (ø)
modules/notification/ui/ui.go	80.55% <0.00%> (-2.78%)	⬇️
modules/process/manager.go	72.50% <0.00%> (-2.50%)	⬇️
services/pull/check.go	47.69% <0.00%> (-2.31%)	⬇️
modules/log/event.go	58.96% <0.00%> (-0.95%)	⬇️
models/notification.go	65.76% <0.00%> (-0.91%)	⬇️
models/error.go	34.85% <0.00%> (-0.34%)	⬇️
modules/notification/mail/mail.go	34.48% <0.00%> (ø)
modules/git/repo.go	46.70% <0.00%> (+0.50%)	⬆️
services/mailer/mail.go	55.91% <0.00%> (+1.07%)	⬆️
... and 4 more

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