fix(store): added noop for all methods in MockReducerManager

[nagyadam2092]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/ngrx/platform/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Documentation has been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

It is currently not possible to use provideMockStore if the component has a dependency to a module which uses the following imports:

• removeFeature
• removeFeatures
• addReducer
• addReducers
• removeReducer
• removeReducers

Currently crashes with something like
TypeError: reducerManager.addReducer is not a function

Closes #2776

What is the new behavior?

Add noop for removeFeature, removeFeatures, addReducer, addReducers, removeReducer, removeReducers.

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

[ngrxbot]

Preview docs changes for 3b50740 at https://previews.ngrx.io/pr2777-3b50740d/

[timdeschryver]

Closes #2776

[timdeschryver]

Thanks @nagyadam2092