Update CHANGELOG.md

Add message about `rb/weak-cryptographic-algorithm`.

Author: aeisenberg

CHANGELOG.md

@@ -2,7 +2,7 @@
 
 ## 2.1.31 - 04 Nov 2022
 
-No user facing changes.
+- The `rb/weak-cryptographic-algorithm` Ruby query has been updated to no longer report uses of hash functions such as `MD5` and `SHA1` even if they are known to be weak. These hash algorithms are used very often in non-sensitive contexts, making the query too imprecise in practice. [#1344](https://github.com/github/codeql-action/pull/1344)
 
 ## 2.1.30 - 02 Nov 2022