Update chromadb and pymilvus versions

Fixing botched merge change.

backend/requirements.txt

@@ -40,8 +40,8 @@ langchain-community==0.2.12
 langchain-chroma==0.1.4
 
 fake-useragent==1.5.1
-chromadb==0.5.5
-pymilvus==2.4.6
+chromadb==0.5.15
+pymilvus==2.4.7
 qdrant-client~=1.12.0
 opensearch-py==2.7.1