docs: Google Drive Loader always set the env var (langchain-ai#14791)

- **Description:** Code written by following, the official documentation
of [Google Drive
Loader](https://python.langchain.com/docs/integrations/document_loaders/google_drive),
gives errors. I have opened an issue regarding this. See langchain-ai#14725. This is
a pull request for modifying the documentation to use an approach that
makes the code work. Basically, the change is that we need to always set
the GOOGLE_APPLICATION_CREDENTIALS env var to an emtpy string, rather
than only in case of RefreshError. Also, rewrote 2 paragraphs to make
the instructions more clear.
- **Issue:** See this related [issue #
14725](langchain-ai#14725)
  - **Dependencies:** NA
  - **Tag maintainer:** @baskaryan
  - **Twitter handle:** NA

Co-authored-by: Snehil <[email protected]>
Co-authored-by: Bagatur <[email protected]>

docs/docs/integrations/document_loaders/google_drive.ipynb

@@ -19,9 +19,11 @@
     "1. `pip install --upgrade google-api-python-client google-auth-httplib2 google-auth-oauthlib`\n",
     "\n",
     "## 🧑 Instructions for ingesting your Google Docs data\n",
-    "By default, the `GoogleDriveLoader` expects the `credentials.json` file to be `~/.credentials/credentials.json`, but this is configurable using the `credentials_path` keyword argument. Same thing with `token.json` - `token_path`. Note that `token.json` will be created automatically the first time you use the loader.\n",
+    "Set the environmental variable `GOOGLE_APPLICATION_CREDENTIALS` to an empty string (`\"\"`).\n",
     "\n",
-    "The first time you use GoogleDriveLoader, you will be displayed with the consent screen in your browser. If this doesn't happen and you get a `RefreshError`, do not use `credentials_path` in your `GoogleDriveLoader` constructor call. Instead, put that path in a `GOOGLE_APPLICATION_CREDENTIALS` environmental variable.\n",
+    "By default, the `GoogleDriveLoader` expects the `credentials.json` file to be located at `~/.credentials/credentials.json`, but this is configurable using the `credentials_path` keyword argument. Same thing with `token.json` - default path: `~/.credentials/token.json`, constructor param: `token_path`.\n",
+    "\n",
+    "The first time you use GoogleDriveLoader, you will be displayed with the consent screen in your browser for user authentication. After authentication, `token.json` will be created automatically at the provided or the default path. Also, if there is already a `token.json` at that path, then you will not be prompted for authentication.\n",
     "\n",
     "`GoogleDriveLoader` can load from a list of Google Docs document ids or a folder id. You can obtain your folder and document id from the URL:\n",
     "\n",