Removed all $that variables
minor #12841 [3.0] Removed all $that variables (saro0h)

This PR was merged into the 3.0-dev branch.

Discussion
----------

[3.0] Removed all $that variables

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | ~
| License       | MIT
| Doc PR        | ~

Commits
-------

7b33d1a Removed all $that variables