governance: let validator vote even if it doesn't have a self-bond (backport #3874)

[mergify]

Describe your changes

Checklist before merging

• If this PR has some consensus breaking changes, I added the corresponding breaking:: labels
  • This will require 2 reviewers to approve the changes
• If this PR requires changes to the docs or specs, a corresponding PR is opened in the namada-docs repo
  • Relevant PR if applies:
• If this PR affects services such as namada-indexer or namada-masp-indexer, a corresponding PR is opened in that repo
  • Relevant PR if applies:

---

This is an automatic backport of pull request #3874 done by [Mergify](https://mergify.com).

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Project coverage is 73.20%. Comparing base (59db279) to head (8ad0c48).
Report is 11 commits behind head on 0.44.0.

Files with missing lines	Patch %	Lines
wasm/tx_vote_proposal/src/lib.rs	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           0.44.0    #3878      +/-   ##
==========================================
- Coverage   73.21%   73.20%   -0.02%     
==========================================
  Files         341      341              
  Lines      105150   105152       +2     
==========================================
- Hits        76987    76977      -10     
- Misses      28163    28175      +12     

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