Remove the deprecated Algorithm.RANGEPREVIEW and QueryType.RANGEPREVIEW members in PyMongo 5.0.

Why these are safe to remove

• Deprecated since 4.9.
• No supported server accepts rangePreview — the server dropped it in 8.0.
• Zero references anywhere under test/. The spec dropped rangePreview long ago, so the resynced spec test corpus contains nothing for it, and no PyMongo test exercises it.
• RANGEPREVIEW appears in exactly two files, both driver source: pymongo/asynchronous/encryption.py (lines 526 and 562) and its generated counterpart pymongo/synchronous/encryption.py.

The members survive only so that existing user code does not fail on import.