Display branch name in delete branch confirmation modal.

[HarshitOnGitHub]

Fixes: #5630.

Screenshots:
Before:

After:

[codecov-io]

Codecov Report

Merging #5654 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #5654      +/-   ##
==========================================
- Coverage   37.85%   37.84%   -0.01%     
==========================================
  Files         322      322              
  Lines       47498    47498              
==========================================
- Hits        17980    17977       -3     
- Misses      26931    26936       +5     
+ Partials     2587     2585       -2

Impacted Files	Coverage Δ
modules/indexer/repo.go	63.35% <0%> (-5.35%)	⬇️
models/repo_indexer.go	48.3% <0%> (-1.7%)	⬇️
routers/repo/view.go	46.01% <0%> (+1.22%)	⬆️
models/repo_list.go	64.55% <0%> (+1.26%)	⬆️
models/unit.go	14.28% <0%> (+14.28%)	⬆️

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