docs(generativeai): update todo comments for quick start guide examples (GoogleCloudPlatform#12597)

## Description

Fixes: [b/362352967](https://b.corp.google.com/362352967)

Note: Before submitting a pull request, please open an issue for discussion if you are not associated with Google.

## Checklist
- [ ] I have followed [Sample Guidelines from AUTHORING_GUIDE.MD](https://togithub.com/GoogleCloudPlatform/python-docs-samples/blob/main/AUTHORING_GUIDE.md)
- [ ] README is updated to include [all relevant information](https://togithub.com/GoogleCloudPlatform/python-docs-samples/blob/main/AUTHORING_GUIDE.md#readme-file)
- [ ] **Tests** pass:   `nox -s py-3.9` (see [Test Environment Setup](https://togithub.com/GoogleCloudPlatform/python-docs-samples/blob/main/AUTHORING_GUIDE.md#test-environment-setup))
- [ ] **Lint** pass:   `nox -s lint` (see [Test Environment Setup](https://togithub.com/GoogleCloudPlatform/python-docs-samples/blob/main/AUTHORING_GUIDE.md#test-environment-setup))
- [ ] These samples need a new **API enabled** in testing projects to pass (let us know which ones)
- [ ] These samples need a new/updated **env vars** in testing projects set to pass (let us know which ones)
- [ ] This sample adds a new sample directory, and I updated the [CODEOWNERS file](https://togithub.com/GoogleCloudPlatform/python-docs-samples/blob/main/.github/CODEOWNERS) with the codeowners for this sample
- [ ] This sample adds a new **Product API**, and I updated the [Blunderbuss issue/PR auto-assigner](https://togithub.com/GoogleCloudPlatform/python-docs-samples/blob/main/.github/blunderbuss.yml) with the codeowners for this sample
- [x] Please **merge** this PR for me once it is approved

Author: msampathkumar

generative_ai/gemini_guide_example.py

@@ -22,7 +22,8 @@ def generate_text() -> str:
 
     from vertexai.generative_models import GenerativeModel, Part
 
-    # TODO(developer): Update project_id and location
+    # TODO(developer): Update & uncomment line below
+    # PROJECT_ID = "your-project-id"
     vertexai.init(project=PROJECT_ID, location="us-central1")
 
     model = GenerativeModel("gemini-1.5-flash-001")

generative_ai/gemini_text_input_example.py

@@ -21,7 +21,7 @@ def generate_from_text_input() -> str:
     import vertexai
     from vertexai.generative_models import GenerativeModel
 
-    # TODO(developer): Update project_id
+    # TODO(developer): Update & uncomment line below
     # PROJECT_ID = "your-project-id"
     vertexai.init(project=PROJECT_ID, location="us-central1")
 

generative_ai/gemini_video_audio.py

@@ -22,7 +22,8 @@ def analyze_video_with_audio() -> str:
     import vertexai
     from vertexai.generative_models import GenerativeModel, Part
 
-    # TODO(developer): Update project_id and location
+    # TODO(developer): Update & uncomment line below
+    # PROJECT_ID = "your-project-id"
     vertexai.init(project=PROJECT_ID, location="us-central1")
 
     model = GenerativeModel("gemini-1.5-flash-001")