Fix: Correct spelling and grammar in tutorial files

I corrected various objective spelling and grammatical errors in:
- tutorial_packaging.rst
- tutorial_scripting.rst
- tutorial_stacks.rst

My changes include fixing typos, removing redundant words,
and improving sentence structure for clarity while adhering
to the constraint of not making subjective style changes or
altering reStructuredText formatting (e.g., double backticks).

Author: google-labs-jules[bot]