[CodeCompletion] Don't suggest initializers on 'AnyObject'
'AnyObject' cannot be instantiated, we shouldn't be providing any
initializers on 'AnyObject' type. 'AnyObject(<HERE>' and global
completions with initializers (i.e. `addinitstotoplevel`) showed all
initializers from objc classes.
Note that, 'lookupVisibleMemberDecls()' on 'AnyObject' (i.e.
'AnyObject.<HERE>') doesn't return initializers even before this change.
But 'QualifiedLookup' did.
rdar://93059166
(cherry picked from commit d32b9c885c44a5a256f1350cc8af1bcc76787c81)
