Fix NEWS: remove removed features from key features list

Remove TCP transport, libcurl-based client transport, and CGI interface
from the key features list -- these were removed in 2.0.0 and must not
be advertised as supported. Add all three to the Removed section.

Also remove libcurl debug logging from Improvements (feature removed)
and renumber the key features list for sequential consistency.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>