Resolve compiler errors in test cases by implicit any

[kwonoj]

RxJS version:

Code to reproduce:

Expected behavior:

Actual behavior:

Additional information:
With latest PR #3019, running tsc on top of repo with tsconfig.json will bring up whole bloat of compilation error by our spec has numbers of implicit any declaration. This is dept we need to pay off and enable those compilation in CI to prevent it happens again.

[kwonoj]

Suggested PR doesn't work, reopen issue.

[kwonoj]

To clarify, to try out this just run tsc on top of repo using base tsconfig.json, not via any other npm scripts in our repo.