Added new task for greener build langchain branch

Author: caseyclements

.evergreen/config.yml

@@ -210,4 +210,16 @@ buildvariants:
     run_on:
       - rhel87-small
     tasks:
-      - name: test-autogen
+      - name: test-autogen
+
+  - name: test-langchain-python-greenerbuild
+    display_name: Langchain Green
+    expansions:
+      DIR: langchain-python
+      REPO_NAME: langchain
+      CLONE_URL: -b ci-on-local-atlas --single-branch https://github.com/caseyclements/langchain.git
+      DATABASE: langchain_test_db
+    run_on:
+      - rhel87-small
+    tasks:
+      - name: test-langchain-python