Fix cltv_expiry_delta comment

[elnosh]

Fix incorrect comment about cltv_expiry_delta.
The cltv_expiry on the outgoing HTLC must be less than the one in the incoming HTLC.

[ldk-reviews-bot]

I've assigned @wpaulino as a reviewer!
I'll wait for their review and will help manage the review process.
Once they submit their review, I'll check if a second reviewer would be helpful.

[ldk-claude-review-bot]

The implementation confirms the PR's changes are correct. The check at channel.rs:11201 is:

htlc.cltv_expiry < outgoing_cltv_value + cltv_expiry_delta

This means outgoing_cltv_value <= incoming_cltv_expiry - cltv_expiry_delta, so the cltv_expiry_delta determines the maximum outgoing value (not minimum), and with incoming=100000, delta=10, outgoing must be at most 99990 (not "at least 100010").

Looking at the diff again: the PR already changes both "minimum" → "maximum" (line 1494) and "at least 100010" → "at most 99990" (line 1496). My prior review comment was a false positive — the PR already correctly fixes line 1494.

No new issues found. The comment corrections are accurate and consistent with the actual implementation.