infra: Sync devcontainer.json and compose file mount location (#20461)

**Sync the config in `devcontainer.json` and `docker-compose.yml`**

Issue: when opening the current `master` branch in a dev container in VS
Code, I get the following message as VS Code cannot find the mounted
source folder:


![image](https://github.com/langchain-ai/langchain/assets/1824461/41cf20c0-d1e0-4648-9578-edf80b99c2db)

Opening in a GitHub Codespace works (it seems to ignore the mounts in
the `docker-compose.yml`.

This PR updates the mount in `docker-compose.yml` and the config in
`devcontainer.json` so that the two align.

I have tested these changes in GitHub Codespaces and a VS Code dev
container and both loaded successfully.

Co-authored-by: Bagatur <22008038+baskaryan@users.noreply.github.com>

.devcontainer/devcontainer.json

@@ -12,7 +12,7 @@
 
 	// The optional 'workspaceFolder' property is the path VS Code should open by default when
 	// connected. This is typically a file mount in .devcontainer/docker-compose.yml
-	"workspaceFolder": "/workspaces/${localWorkspaceFolderBasename}",
+	"workspaceFolder": "/workspaces/langchain",
 
 	// Prevent the container from shutting down
 	"overrideCommand": true

.devcontainer/docker-compose.yaml

@@ -6,7 +6,7 @@ services:
       context: ..
     volumes:
    # Update this to wherever you want VS Code to mount the folder of your project
-      - ..:/workspaces:cached
+      - ..:/workspaces/langchain:cached
     networks:
       - langchain-network 
   #   environment: