[jest-haste-map] Remove mapper option.

[cpojer]

Summary

This option was added a while back to support some use-cases with Yarn PnP but it was neither documented nor is this how I would solve the problem of files not being materialized as this functionality has the potential to de-opt operations in Jest's haste map.

This PR removes the option.

Test plan

yolo

[thymikee]

cc @arcanis

[arcanis]

Thanks for the ping - Yarn doesn't rely on this option, lgtm 👍

[codecov-io]

Codecov Report

Merging #9581 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #9581      +/-   ##
==========================================
+ Coverage   65.07%   65.08%   +<.01%     
==========================================
  Files         286      286              
  Lines       12144    12137       -7     
  Branches     3010     3007       -3     
==========================================
- Hits         7903     7899       -4     
+ Misses       3605     3604       -1     
+ Partials      636      634       -2

Impacted Files	Coverage Δ
packages/jest-haste-map/src/index.ts	81.26% <ø> (ø)	⬆️
packages/jest-haste-map/src/crawlers/watchman.ts	88.65% <100%> (+0.19%)	⬆️
packages/expect/src/utils.ts	96.22% <0%> (+1.25%)	⬆️

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