add proposal for modify the MaxGasUsedPerBlock

[lyh169]

• 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.

• [ ] Wrote tests

• [ ] Updated relevant documentation (docs/)

• [ ] Added a relevant changelog entry to the Unreleased section in CHANGELOG.md

• [ ] Reviewed Files changed in the github PR explorer

---

For Admin Use:

• Added appropriate labels to PR (ex. wip, ready-for-review, docs)
• Reviewers Assigned
• Squashed all commits, uses message "Merge PR #XYZ: [title]" (coding standards)

[codecov-commenter]

Codecov Report

Merging #3241 (5301f46) into dev (f438319) will decrease coverage by 0.01%. The diff coverage is 28.57%.

:exclamation: Current head 5301f46 differs from pull request most recent head 49e98bf. Consider uploading reports for the commit 49e98bf to get more accurate results

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@@            Coverage Diff             @@
##              dev    #3241      +/-   ##
==========================================
- Coverage   36.57%   36.57%   -0.01%     
==========================================
  Files         444      445       +1     
  Lines       46663    46705      +42     
==========================================
+ Hits        17067    17081      +14     
- Misses      28330    28359      +29     
+ Partials     1266     1265       -1     

Files Changed	Coverage Δ
app/config/config.go	26.71% <0.00%> (-0.17%)	:arrow_down:
x/params/querier.go	0.00% <0.00%> (ø)
x/params/types/params.go	0.00% <0.00%> (ø)
x/params/types/params_block.go	0.00% <0.00%> (ø)
app/app.go	81.31% <100.00%> (+0.13%)	:arrow_up:
x/params/keeper.go	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes