[PR #7201/63db4a58 backport][3.9] Drop unused mypy-extensions

[patchback]

This is a backport of PR #7201 as merged into master (63db4a5).

None

[codecov]

Codecov Report

Merging #7202 (d23beb6) into 3.9 (9cffef0) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##              3.9    #7202   +/-   ##
=======================================
  Coverage   97.35%   97.35%           
=======================================
  Files         107      107           
  Lines       31276    31276           
  Branches     3963     3963           
=======================================
  Hits        30449    30449           
  Misses        621      621           
  Partials      206      206           

Flag	Coverage Δ
CI-GHA	97.25% <ø> (ø)
OS-Linux	96.92% <ø> (ø)
OS-Windows	94.51% <ø> (+<0.01%)	⬆️
OS-macOS	96.48% <ø> (ø)
Py-3.10.9	96.97% <ø> (ø)
Py-3.11.0	95.38% <ø> (+<0.01%)	⬆️
Py-3.7.15	96.72% <ø> (ø)
Py-3.7.9	94.36% <ø> (ø)
Py-3.8.10	94.28% <ø> (ø)
Py-3.8.16	96.62% <ø> (ø)
Py-3.9.13	94.28% <ø> (+<0.01%)	⬆️
Py-3.9.16	96.64% <ø> (ø)
Py-pypy7.3.11	94.05% <ø> (-0.01%)	⬇️
VM-macos	96.48% <ø> (ø)
VM-ubuntu	96.92% <ø> (ø)
VM-windows	94.51% <ø> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more