Add v0.38.1 changelog entry

[alexanderbez]

---

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

---

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]" (coding standards)

[codecov]

Codecov Report

Merging #5633 into master will decrease coverage by 3.59%.
The diff coverage is 58.62%.

@@            Coverage Diff            @@
##           master    #5633     +/-   ##
=========================================
- Coverage   44.64%   41.05%   -3.6%     
=========================================
  Files         324      325      +1     
  Lines       24709    26922   +2213     
=========================================
+ Hits        11031    11052     +21     
- Misses      12618    14810   +2192     
  Partials     1060     1060

Impacted Files	Coverage Δ
x/distribution/types/proposal.go	11.11% <ø> (ø)	⬆️
x/distribution/types/fee_pool.go	100% <ø> (ø)	⬆️
x/distribution/types/msg.go	56.92% <ø> (ø)	⬆️
x/distribution/types/params.go	45.2% <ø> (ø)	⬆️
x/distribution/types/delegator.go	0% <ø> (ø)	⬆️
x/distribution/types/types.pb.go	0.72% <ø> (ø)
x/distribution/keeper/invariants.go	0% <0%> (ø)	⬆️
x/distribution/genesis.go	0% <0%> (ø)	⬆️
x/distribution/keeper/hooks.go	30.23% <0%> (ø)	⬆️
x/distribution/types/validator.go	0% <0%> (ø)	⬆️
... and 12 more