Revert "Not yet supported" section from README.md

Reverts the README addition from f715bf7. Two reasons: (1) the
section was added by editing README.md directly, but README.md
is generated from notebooks/readme.clj -- direct edits get
clobbered on regen. (2) On reflection the list of three items
(dual y-axes, rolling stats, Q-Q) is far from comprehensive
and not particularly helpful as a teaser of what's missing.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: daslu

README.md

@@ -70,13 +70,6 @@ Scatter plot matrix (SPLOM) — all pairwise combinations with color grouping:
 ![](readme_files/image2.svg)
 
 
-## Not yet supported
-
-A few common plotting tasks are not yet covered: dual y-axes,
-rolling-window statistics (compute the column externally before
-plotting), and Q-Q or other diagnostic plots.
-
-
 ## Documentation
 
 [Full documentation](https://scicloj.github.io/plotje/)