チャンネルページでisArchivedを明確に表示するように

[Npepperlinux]

• チャンネルがアーカイブされている場合に、「このチャンネルはアーカイブされています」と表示されるようにしました。また、ノートボタンが表示されなくなりました（Thanks @4ster1sk !）
  

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 50.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 27.69%. Comparing base (6955662) to head (2af2092).
Report is 1 commits behind head on develop.

Files with missing lines	Patch %	Lines
lib/view/channels_page/channel_detail_info.dart	50.00%	3 Missing ⚠️

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Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #671   +/-   ##
========================================
  Coverage    27.69%   27.69%           
========================================
  Files          312      312           
  Lines        16253    16258    +5     
========================================
+ Hits          4501     4503    +2     
- Misses       11752    11755    +3     

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[4ster1sk]

書き込みボタン非表示はChannelDetailFloatingActionButtonのAsyncData(:final value)でComminityChannelとれるのでそのへんでいい感じにすれば良さそう