doc: add release note for #25574

Author: mzumsande

doc/release-notes-25574.md

@@ -0,0 +1,13 @@
+Updated settings
+----------------
+
+If the `-checkblocks` or `-checklevel` options are explicitly provided by the
+user, but the verification checks cannot be completed due to an insufficient
+dbcache, Bitcoin Core will now return an error at startup. (#25574)
+
+RPC
+---
+The `-verifychain` RPC will now return `false` if the checks didn't fail,
+but couldn't be completed at the desired depth and level. This could be due
+to missing data while pruning, due to an insufficient dbcache or due to
+the node being shutdown before the call could finish. (#25574)