Support RxJS v7 about reactive-forms

[wSedlacek]

🤔 After looking at the code it seems that rxjs is not intended to be a dependency of reactive-forms at all.

When I build the package with nx build reactive-forms I get the follow peer dependencies.

  "peerDependencies": {
    "@angular/forms": ">= 13.0.0",
    "@angular/core": "13.0.2"
  },

However when I install the package from npm it has the following dependencies.

  "peerDependencies": {
    "@angular/forms": ">= 13.0.0",
    "rxjs": "~6.6.0",
    "@angular/core": "13.0.2"
  },

This is interesting because the only commit since the 4.0.0 commit was
3adcf11

Perhaps this is an issue of an outdated nx CLI being used to build and publish?
Or perhaps there is some dependency cache going on the CI?