Change slack links to chat ones

[Solexplorer]

Description

Changed links to redirect to chat instead of slack

Refers/Fixes

Testing

PR so small, are tests needed?

[codecov]

Codecov Report

Merging #6747 into master will increase coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #6747      +/-   ##
==========================================
+ Coverage   26.70%   26.72%   +0.02%     
==========================================
  Files         293      293              
  Lines       27845    27845              
  Branches     4108     4108              
==========================================
+ Hits         7435     7441       +6     
+ Misses      20139    20138       -1     
+ Partials      271      266       -5     

Impacted Files	Coverage Δ
app/dashboard/notifications.py	17.15% <ø> (ø)
app/quests/views.py	16.22% <0.00%> (ø)
app/dashboard/views.py	10.78% <0.00%> (ø)
...rketing/management/commands/no_applicants_email.py	0.00% <0.00%> (ø)
...eting/management/commands/assemble_leaderboards.py	39.83% <0.00%> (ø)
app/dashboard/embed.py	31.60% <0.00%> (+3.44%)	⬆️

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[danlipert]

@Solexplorer just so you know, the testing section the PR doesn't require you to write tets, but rather just explain how it was tested - that could be via included unit tests, or you could just write that it doesnt need testing because its so simple, or the change isn't in the application itself, or you can add a video showing the results of your changes :)