"auth/StdTx" -> "cosmos-sdk/StdTx"

[jordaaash]

• 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

• Re-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 pull request #XYZ: [title]" (coding standards)

[alexanderbez]

ACK

[codecov]

Codecov Report

Merging #5255 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #5255   +/-   ##
======================================
  Coverage    53.5%   53.5%           
======================================
  Files         290     290           
  Lines       17770   17770           
======================================
  Hits         9507    9507           
  Misses       7513    7513           
  Partials      750     750