Fix Module not found: Error: Can't resolve 'react' errors

See: apollographql/apollo-client#7318 (comment)

projects/demo/src/app/app.module.ts

@@ -18,7 +18,7 @@ import { MatListModule } from '@angular/material/list';
 
 import { APOLLO_OPTIONS } from 'apollo-angular';
 import { HttpLink } from 'apollo-angular/http';
-import { InMemoryCache } from '@apollo/client';
+import { InMemoryCache } from '@apollo/client/core';
 
 import { AppRoutingModule } from './app-routing.module';
 import { AppComponent } from './app.component';