Update Berlin conference banner (#2454)

This just notes the conf dates now that we're closer.
I'm open to other appraoches,
perhaps something like `starting soon!`?

Author: ericholscher

docs/conf.py

@@ -219,7 +219,7 @@ def _load_data(self, env, data_source, encoding):
 announcement_message = None
 
 if datetime.date(2025, 8, 19) <= datetime.date.today() <= datetime.date(2025, 10, 28):
-    announcement_message = "Berlin 2025 speakers announced. <a href='/conf/berlin/2025/'>View the conference site</a>."
+    announcement_message = "Berlin conference: Oct 27-28. <a href='/conf/berlin/2025/'>View the conference site</a>."
 
 html_context = {
     'conf_py_root': os.path.dirname(os.path.abspath(__file__)),