Fixed important typo causing installation issues.

This was passing 'mocks' to the `installModule` function, which then erroneously generated installation documentation saying one should install this as 'ngMocks' in their dependencies. This is incorrect. The module name is actually 'ngMock'. Angular will throw an exception saying it can't find 'ngMocks'. But it finds the correct files with 'ngMock'. I personally ran into this issue, so wanted to fix it.