Indicate WordPress 6.9 compatibility.

Signed-off-by: Peter Wilson <git-commit-by@peterwilson.cc>

Author: peterwilsoncc

readme.txt

@@ -1,7 +1,7 @@
 === Simple Search Submission for IndexNow ===
 Contributors: peterwilsoncc
 Tags: seo, indexnow, crawling
-Tested up to: 6.8
+Tested up to: 6.9
 Stable tag: 1.2.0
 License: GPL-2.0-or-later
 License URI: https://github.com/peterwilsoncc/simple-search-submission/blob/main/LICENSE