enforce should not prevent using minChunks etc. on cacheGroup

[sokra]

Partial revert "enforce doesn't affect minSize for maxSize" #8451

What kind of change does this PR introduce?
bugfix

Did you add tests for your changes?
yes

Does this PR introduce a breaking change?
It reverts an accidental breaking introduces by #8451

What needs to be documented once your changes are merged?
The splitChunks.enforce documentation is incorrect.
It should be stated that enforce sets minChunks: 1, minSize: 0 and maxInitial/AsyncRequests: Infinity, but it's supported that this can be overriden by the same property on the cacheGroup

[webpack-bot]

For maintainers only:

• This need to be documented (issue in webpack/webpack.js.org will be filed when merged)

[webpack-bot]

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