chore(deps): update dependency langchain to v0.2.0

requirements.txt

@@ -32,7 +32,7 @@ idna==3.6; python_version >= '3.5'
 jsonpatch==1.33; python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6'
 jsonpointer==2.4; python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6'
 l18n==2021.3
-langchain==0.0.352; python_version < '4.0' and python_full_version >= '3.8.1'
+langchain==0.2.0; python_version < '4.0' and python_full_version >= '3.8.1'
 langchain-community==0.0.6; python_version < '4.0' and python_full_version >= '3.8.1'
 langchain-core==0.1.3; python_version < '4.0' and python_full_version >= '3.8.1'
 langsmith==0.0.75; python_version < '4.0' and python_full_version >= '3.8.1'