Enable download button for offline tutorial access - Fixes #712

Enables the download_all_examples feature in Sphinx gallery configuration
to allow users to download tutorials for offline access.

Issue:
Users requested the ability to access PyTorch tutorials offline (e.g., before
flights) without having to build the entire repository locally, which takes
a long time.

Solution:
Changed download_all_examples from False to True in conf.py. This enables
download buttons on all tutorial pages, allowing users to:
- Download individual tutorial files
- Access tutorials offline
- Save tutorials for later reference

Benefits:
- Improves accessibility for users with limited internet
- Enables offline learning and development
- Reduces barrier to entry (no need to build repo)
- Aligns with common documentation practices

This is a simple one-line configuration change that significantly improves
user experience for offline access to PyTorch tutorials.

Fixes #712

Author: 0xsatoshi99

conf.py

@@ -175,7 +175,7 @@ def wrapper(*args, **kwargs):
     "promote_jupyter_magic": True,
     "backreferences_dir": None,
     "write_computation_times": True,
-    "download_all_examples": False,
+    "download_all_examples": True,
     "show_signature": False,
     "first_notebook_cell": (
         "# For tips on running notebooks in Google Colab, see\n"