gov: fix parameter change proposals

[dshe-certik]

Related: #146

Description

This work was initialized by @ziyi-zhang-1130 and was targeting to have claim proposals fully tested by increasing number of passed proposals in simulations.

However, we found this update exposed some problems with parameter change proposals, so we made it an independent PR and will try to fix parameter change proposals in this PR.

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For contributor use:

• 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

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For admin use:

• Added appropriate labels to PR (ex. WIP, R4R, docs, etc)
• Reviewers assigned
• Squashed all commits, uses message "Merge pull request #XYZ: [title]"

[ziyi-zhang-1130]

Will look into this 🧐

[codecov-io]

Codecov Report

Merging #145 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #145   +/-   ##
=======================================
  Coverage   53.76%   53.76%           
=======================================
  Files          49       49           
  Lines        3383     3383           
=======================================
  Hits         1819     1819           
  Misses       1432     1432           
  Partials      132      132