deps: fix dependency on celestia-app

[tuxcanfly]

Overview

This PR fixes dependency hell introduced due to celestia-app namespace package in #55

Checklist

• New and updated code has appropriate documentation
• New and updated code has new and/or updated testing
• Required CI checks are passing
• Visual proof for any user facing features like CLI or documentation updates
• Linked issues closed with keywords

[codecov-commenter]

Codecov Report

Merging #56 (5a17588) into main (e91b08a) will decrease coverage by 17.92%.
The diff coverage is 21.97%.

@@             Coverage Diff             @@
##             main      #56       +/-   ##
===========================================
- Coverage   55.05%   37.14%   -17.92%     
===========================================
  Files           2        3        +1     
  Lines          89      175       +86     
===========================================
+ Hits           49       65       +16     
- Misses         34       97       +63     
- Partials        6       13        +7     

Impacted Files	Coverage Δ
namespace.go	18.60% <18.60%> (ø)
client.go	52.38% <80.00%> (ø)