x/gov v0.43 Audit updates

[amaury1093]

Description

some small improvements that I found while auditing x/gov.

ref: #9218

---

Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• Targeted PR against correct branch (see CONTRIBUTING.md)
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the module structure standards.
• Wrote unit and integration tests
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added relevant godoc comments.
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer
• Review Codecov Report in the comment section below once CI passes

[codecov]

Codecov Report

Merging #9258 (e0fa31f) into master (4af85dc) will increase coverage by 0.01%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #9258      +/-   ##
==========================================
+ Coverage   60.28%   60.30%   +0.01%     
==========================================
  Files         591      591              
  Lines       36937    36937              
==========================================
+ Hits        22269    22276       +7     
+ Misses      12698    12691       -7     
  Partials     1970     1970              

Impacted Files	Coverage Δ
x/gov/client/cli/tx.go	17.85% <0.00%> (ø)
x/gov/types/proposal.go	19.78% <0.00%> (ø)
x/gov/types/msgs.go	49.03% <0.00%> (+1.92%)	⬆️
x/gov/keeper/deposit.go	76.47% <0.00%> (+5.88%)	⬆️

[blushi]

Looks good to me!

[atheeshp]

LGTM