Fix debug.ts __debugKind check

[jakebailey]

Fixes my oops in #50422.

The old code was:

if (!ctor.prototype.hasOwnProperty("__debugKind")) { ... }

Which I changed to:

if (!hasProperty(ctor, "__debugKind")) { ... }

But it should have been:

if (!hasProperty(ctor.prototype, "__debugKind")) { ... }

[DanielRosenwasser]

Thanks!