Update Slashing Spec

[alexanderbez]

This PR is not a complete refactor and cleanup of the existing slashing specs, but rather focuses on:

• Cleaning up and fixing markdown
• Usage of correct parameter names
• Helping clarifying certain concepts focusing on liveness

ref: #4628

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• 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: clog add [section] [-t <tag>] [-m <msg>]

• Re-reviewed Files changed in the github PR explorer

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For Admin Use:

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

[codecov]

Codecov Report

Merging #4892 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #4892   +/-   ##
=======================================
  Coverage   54.04%   54.04%           
=======================================
  Files         269      269           
  Lines       17130    17130           
=======================================
  Hits         9258     9258           
  Misses       7184     7184           
  Partials      688      688