refactor(core): remove isObservable TODO (#39669)
refactor(core): remove isObservable TODO (#39669)

This commit removes the TODO comment that proposed
that we use the built-in RxJS `isObservable()` function.

This is not a viable approach since the built-in function
requires that the `obj` contains additional methods that
our "observable" types (such as `EventEmitter`) do not
necessarily have.

See #39643 for more information.

PR Close #39669

manekinekko/angular,IdeaBlade/angular,blesh/angular,mgechev/angular,ocombe/angular,ocombe/angular,ocombe/angular,angular/angular,angular-indonesia/angular,manekinekko/angular,angular-indonesia/angular,alxhub/angular,brandonroberts/angular,IdeaBlade/angular,ocombe/angular,brandonroberts/angular,gkalpak/angular,IdeaBlade/angular,JiaLiPassion/angular,brandonroberts/angular,shairez/angular,blesh/angular,angular/angular,manekinekko/angular,IdeaBlade/angular,mgechev/angular,brandonroberts/angular,blesh/angular,gnomeontherun/angular,IdeaBlade/angular,blesh/angular,gnomeontherun/angular,gkalpak/angular,JiaLiPassion/angular,alxhub/angular,shairez/angular,shairez/angular,shairez/angular,blesh/angular,brandonroberts/angular,angular/angular,angular-indonesia/angular,angular/angular,gkalpak/angular,alxhub/angular,JiaLiPassion/angular,gnomeontherun/angular,angular-indonesia/angular,JiaLiPassion/angular,mgechev/angular,ocombe/angular,mgechev/angular,manekinekko/angular,shairez/angular,gkalpak/angular,brandonroberts/angular,mgechev/angular,alxhub/angular,ocombe/angular,gnomeontherun/angular,manekinekko/angular,manekinekko/angular,alxhub/angular