chore: remove TerserPlugin step for build

[mistercrunch]

SUMMARY

Trying webpack without TerserPlugin, there doesn't seem to be any impact on the bundle size, yet we save a bunch of cpu time on the npm run build step. To be fair, when I don't remove the .terser-plugin-cache/, the difference is minimal, but assuming docker isn't doing anything special to keep that cache active, in that context, or in the context of a new env, the hit is pretty significant. This only affect npm run build but could shave a few minutes from some of our builds.

Methodology

# timing with
$ time npm run build

# cleanup between steps
$ rm -rf .terser-plugin-cache/
$ rm -rf ../superset/static/assets/*

With Terser

$ du -sh ../superset/static/assets/
 54M    ../superset/static/assets/

# first run
real    2m17.742s
user    9m2.984s
sys     0m50.677s

# second run
real    2m31.410s
user    9m16.850s
sys     0m47.766s

Without Terser

$ rm .terser*
$ du -sh ../superset/static/assets/
 54M    ../superset/static/assets/

# first run
real    1m12.785s
user    3m50.063s
sys     0m26.636s

# second run
real    1m35.231s
user    4m54.031s
sys     0m38.375s

[codecov]

Codecov Report

Merging #16163 (e4e95aa) into master (3712ee0) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #16163   +/-   ##
=======================================
  Coverage   76.81%   76.81%           
=======================================
  Files         996      996           
  Lines       52942    52942           
  Branches     6734     6734           
=======================================
  Hits        40668    40668           
  Misses      12049    12049           
  Partials      225      225           

Flag	Coverage Δ
javascript	71.19% <ø> (ø)

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[zhaoyongjie]

https://webpack.js.org/plugins/terser-webpack-plugin/
Webpack v5 or above don't need to install TerserPlugin

LGTM