fix(jsdom-env): remove Buffer

[SimenB]

Summary

Following up on #11222. For some reason a JSDOM test takes about 12 seconds rather than less than 1 with this change. (slow enough that a test fails since it crosses the test length threshold, causing a snapshot diff)

Test plan

Green CI, eventually

[MichaelDeBoey]

This test should be deleted too I think?
https://github.com/facebook/jest/blob/167aad4565f6960968a8666d78234ed198fa0770/e2e/env-test/__tests__/equivalent.test.js#L15-L20

[codecov-io]

Codecov Report

Merging #11241 (167aad4) into master (167aad4) will not change coverage.
The diff coverage is n/a.

❗ Current head 167aad4 differs from pull request most recent head 412360d. Consider uploading reports for the commit 412360d to get more accurate results

@@           Coverage Diff           @@
##           master   #11241   +/-   ##
=======================================
  Coverage   64.24%   64.24%           
=======================================
  Files         308      308           
  Lines       13502    13502           
  Branches     3289     3289           
=======================================
  Hits         8675     8675           
  Misses       4117     4117           
  Partials      710      710           

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