Stop ignoring figures in the slides template

The unrooted *.pdf and *.png rules hid anything added under figures/.
Build products are all at the document root, so the rooted rules are
enough.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

slides_template/.gitignore

@@ -1,27 +1,18 @@
+# Build products, at the document root only, so figures/ is left alone.
 /auto/
 /vc
+/notes.config
 /*.aux
-/*.log
-/*.out
-/*.pdf
 /*.fdb_latexmk
 /*.fls
-/*.ttt
+/*.log
 /*.nav
-/*.toc
+/*.notes
+/*.out
+/*.pdf
 /*.snm
+/*.toc
+/*.ttt
 /*.xdv
-/notes.config
-*.aux
-*.fdb_latexmk
-*.fls
-*.log
-*.nav
-*.notes
-*.out
-*.snm
-*.toc
-*.pdf
-*.png
-*-luamml-mathml.html
+/*-luamml-mathml.html
 *.swp