Problem: unsafe experimental flag is not needed

[thomas-nguy]

👮🏻👮🏻👮🏻 !!!! REFERENCE THE PROBLEM YOUR ARE SOLVING IN THE PR TITLE AND DESCRIBE YOUR SOLUTION HERE !!!! DO NOT FORGET !!!! 👮🏻👮🏻👮🏻

Remove unsafe experimental flag

PR Checklist:

• Have you read the CONTRIBUTING.md?
• Does your PR follow the C4 patch requirements?
• Have you rebased your work on top of the latest master?
• Have you checked your code compiles? (make)
• Have you included tests for any non-trivial functionality?
• Have you checked your code passes the unit tests? (make test)
• Have you checked your code formatting is correct? (go fmt)
• Have you checked your basic code style is fine? (golangci-lint run)
• If you added any dependencies, have you checked they do not contain any known vulnerabilities? (go list -json -m all | nancy sleuth)
• If your changes affect the client infrastructure, have you run the integration test?
• If your changes affect public APIs, does your PR follow the C4 evolution of public contracts?
• If your code changes public APIs, have you incremented the crate version numbers and documented your changes in the CHANGELOG.md?
• If you are contributing for the first time, please read the agreement in CONTRIBUTING.md now and add a comment to this pull request stating that your PR is in accordance with the Developer's Certificate of Origin.

Thank you for your code, it's appreciated! :)

[mmsqe]

do we still keep package experimental and seems still have experimental in test_helpers

[codecov]

Codecov Report

Merging #834 (cbb19e9) into main (eeb5af9) will increase coverage by 0.42%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main     #834      +/-   ##
==========================================
+ Coverage   33.89%   34.32%   +0.42%     
==========================================
  Files          30       30              
  Lines        1599     1579      -20     
==========================================
  Hits          542      542              
+ Misses       1000      980      -20     
  Partials       57       57              

Impacted Files	Coverage Δ
app/genesis.go	0.00% <0.00%> (ø)
app/state.go	0.00% <0.00%> (ø)
app/upgrades.go	0.00% <0.00%> (ø)
x/cronos/module.go	53.84% <ø> (+0.68%)	⬆️

[calvinaco]

LGTM, left a comment on the upgrade handler