Change banner for the next hackathon

[Solexplorer]

Description

Changes the top banner for the Sustain Web3 Hackathon

Refers/Fixes

Testing

Pr so small, doesn't need testing

[codecov]

Codecov Report

Merging #5895 into master will increase coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #5895      +/-   ##
==========================================
+ Coverage    29.5%   29.53%   +0.02%     
==========================================
  Files         265      265              
  Lines       22871    22871              
  Branches     3320     3320              
==========================================
+ Hits         6748     6754       +6     
+ Misses      15845    15839       -6     
  Partials      278      278

Impacted Files	Coverage Δ
app/dashboard/embed.py	31.6% <0%> (+3.44%)	⬆️

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