Replace concat(Immutable) with Immutable as item of plugins array

[pedrottimark]

Summary

Follow up after #4189

Test plan

Separating from previous PR should avoid problem with links to dependencies

[codecov-io]

Codecov Report

Merging #4207 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master    #4207   +/-   ##
=======================================
  Coverage   60.18%   60.18%           
=======================================
  Files         191      191           
  Lines        6763     6763           
  Branches        6        6           
=======================================
  Hits         4070     4070           
  Misses       2690     2690           
  Partials        3        3

Impacted Files	Coverage Δ
packages/jest-diff/src/index.js	80.48% <ø> (ø)	⬆️
packages/jest-matcher-utils/src/index.js	100% <ø> (ø)	⬆️
packages/jest-snapshot/src/plugins.js	100% <100%> (ø)	⬆️

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[github-actions]

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