Fix 22668 - Don't error when a deprecated method overrides another one

[MoonlightSentinel]

Because both declarations acknowledge that the declaration is deprecated.
This is especially important for libraries that provide a collection of
classes and want to deprecate certain method(s) throughout the entire
class hierarchy.

[dlang-bot]

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	22668	normal	Deprecation when a deprecated method overrides another deprecated method

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "master + dmd#13533"