fix(examples): Instantiate Session before reading account/region in optimize-example

[Hannah14295]

optimize-example.ipynb called Session.account_id() and Session.boto_region_name on the Session class, raising 'TypeError: account_id() missing 1 required positional argument: self'. Create a Session instance first and read the values from it.

Issue #, if available:
N/A

Description of changes:
optimize-example.ipynb called Session.account_id() and Session.boto_region_name
on the Session class instead of an instance, so the first Configuration cell
failed with:

TypeError: account_id() missing 1 required positional argument: 'self'

This creates a Session() instance first and reads account_id() / boto_region_name
from it. No functional change beyond fixing the crash.

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