chore(deps): update dependency langchain-core to v0.2.12 (#79)

Co-authored-by: Averi Kitsch <akitsch@google.com>

Author: renovate-bot

requirements.txt

@@ -1,3 +1,3 @@
-langchain-core==0.2.11
+langchain-core==0.2.12
 langchain-community==0.2.6
 google-cloud-spanner==3.47.0