chore(init): remove --force flag

[jamesgeorge007]

What kind of change does this PR introduce?
chore

Did you add tests for your changes?
Remove stale tests.

If relevant, did you update the documentation?
Yup.

Summary
webpack init generates a webpack-config file by default, and the --force flag doesn't serve any purpose.

Does this PR introduce a breaking change?
The --force flag isn't recognized anymore.

Other information
N/A

[codecov]

Codecov Report

Merging #2391 (af5f4f7) into master (9d6dbda) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #2391   +/-   ##
=======================================
  Coverage   71.26%   71.27%           
=======================================
  Files          46       46           
  Lines        2158     2155    -3     
  Branches      570      568    -2     
=======================================
- Hits         1538     1536    -2     
+ Misses        620      619    -1     

Impacted Files	Coverage Δ
...kages/generators/src/utils/modify-config-helper.ts	57.14% <100.00%> (-0.76%)	⬇️
packages/generators/src/utils/scaffold.ts	77.55% <100.00%> (+1.08%)	⬆️
packages/init/src/index.ts	88.88% <100.00%> (ø)

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