chore: use octicon-mirror for feeds display

[BLumia]

This patch changes the feeds icon for mirror type actions from octicon-repo-clone to octicon-mirror, since the icon for mirror type repo on the repo page already changed to octicon-mirror in 1.13.0.

[codecov-io]

Codecov Report

Merging #13928 (0f612cd) into master (ccfa408) will decrease coverage by 0.13%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master   #13928      +/-   ##
==========================================
- Coverage   42.24%   42.10%   -0.14%     
==========================================
  Files         710      710              
  Lines       77232    77232              
==========================================
- Hits        32626    32518     -108     
- Misses      39241    39362     +121     
+ Partials     5365     5352      -13     

Impacted Files	Coverage Δ
modules/templates/helper.go	49.45% <0.00%> (ø)
modules/indexer/stats/queue.go	52.94% <0.00%> (-23.53%)	⬇️
modules/notification/ui/ui.go	84.72% <0.00%> (-11.12%)	⬇️
modules/notification/mail/mail.go	33.33% <0.00%> (-9.20%)	⬇️
models/issue_comment.go	43.50% <0.00%> (-8.92%)	⬇️
modules/indexer/stats/db.go	43.47% <0.00%> (-8.70%)	⬇️
modules/queue/unique_queue_channel.go	58.06% <0.00%> (-6.46%)	⬇️
modules/git/commit.go	49.67% <0.00%> (-3.95%)	⬇️
modules/git/utils.go	73.77% <0.00%> (-3.28%)	⬇️
modules/notification/base/null.go	74.28% <0.00%> (-2.86%)	⬇️
... and 13 more

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[techknowlogick]

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