docs: mark webpack-cli 4.7.0 as min version for dev server v4

[anshumanv]

• This is a bugfix
• This is a feature
• This is a code refactor
• This is a test update
• This is a docs update
• This is a metadata update

For Bugs and Features; did you add new tests?

NA

Motivation / Use-Case

It seems some problems with webpack-cli v4.6.0 so marking 4.7.0 as minimum supported version #3682 (comment)

Breaking Changes

no

Additional Info

[codecov]

Codecov Report

Merging #3727 (772d2ab) into master (804b868) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #3727   +/-   ##
=======================================
  Coverage   93.20%   93.20%           
=======================================
  Files          15       15           
  Lines        1324     1324           
  Branches      458      458           
=======================================
  Hits         1234     1234           
  Misses         83       83           
  Partials        7        7           

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