Revert changes for keybase encoding.

[jgimeno]

Revert some changes done here:

#5799

Description

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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
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[alexanderbez]

ACK, can you confirm @alessio?

[jgimeno]

@alexanderbez I added a comment for the breaking client on the changelog.

[alessio]

Just a request for an additional test case. Looks good otherwise

[codecov]

Codecov Report

Merging #5814 into master will not change coverage.
The diff coverage is 66.66%.

@@           Coverage Diff           @@
##           master    #5814   +/-   ##
=======================================
  Coverage   36.03%   36.03%           
=======================================
  Files         342      342           
  Lines       34782    34782           
=======================================
  Hits        12534    12534           
  Misses      20998    20998           
  Partials     1250     1250

Impacted Files	Coverage Δ
crypto/keys/keybase_base.go	72.51% <0%> (ø)	⬆️
crypto/keys/types.go	80.72% <100%> (ø)	⬆️