prepare release v1.5.3

CHANGELOG.md

@@ -9,7 +9,7 @@ Operators, you should copy/paste content of this content straight to your projec
 If you were at `firehose-core` version `1.0.0` and are bumping to `1.1.0`, you should copy the content between those 2 version to your own repository, replacing placeholder value `fire{chain}` with your chain's own binary.
 
 
-## v1.5.3 (Unreleased)
+## v1.5.3
 
 * fix "hub" not recovering on certain disconnections in relayer/firehose/substreams (scenarios requiring full restart)