Various UI fixes

[CirnoT]

• Fixes Commit body on commit view is missing padding-bottom #14238
• Fixes Border around buttons on confirmation modal are not visible #14235
• Fixes Some actions are missing padding-bottom on dashboard view #14237
• Fixes Organization visibility uses icon instead of label on explore page #14234
• Fixes Key icon is misaligned on 'Authorized OAuth2 Applications' #14232
• Fixes 'Show resolved' link on conversations on diff view is misaligned #14236
• Use octicon to show private status of repo in admin dashboard

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@4092c04). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master   #14239   +/-   ##
=========================================
  Coverage          ?   41.97%           
=========================================
  Files             ?      735           
  Lines             ?    78933           
  Branches          ?        0           
=========================================
  Hits              ?    33134           
  Misses            ?    40345           
  Partials          ?     5454           

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