[webkit checkers] Treat WK's WeakObjCPtr::getAutoreleased() return value as safe

[csaavedra]

The value is returned via objc_loadWeak(), which is a retained and autoreleased weak reference, so it should be treated as safe.

cc @rniwa

[rniwa]

Fixing this in #161236

[llvmbot]

@llvm/issue-subscribers-clang-static-analyzer

Author: Claudio Saavedra (csaavedra)

The value is returned via `objc_loadWeak()`, which is a retained and autoreleased weak reference, so it should be treated as safe.

cc @rniwa