ci: use clang-16 for Valgrind

Switch to Ubuntu Noble.

contrib/valgrind.supp

@@ -13,8 +13,8 @@
 #
 # Note that suppressions may depend on OS and/or library versions.
 # Tested on:
-# * aarch64 (Debian Bookworm system libs, clang, without gui)
-# * x86_64  (Debian Bookworm system libs, clang, without gui)
+# * aarch64 (Ubuntu Noble system libs, clang, without gui)
+# * x86_64  (Ubuntu Noble system libs, clang, without gui)
 {
    Suppress libdb warning - https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=662917
    Memcheck:Cond