fix(docs/typography-guide): Defining a level

[atrawally]

fix(docs/typography-guide): Defining a level

Fixes a bug in the Topography Guide where a function was incorrectly named. Replaces 'define-topography-config' with 'define-topography-level'

Fixes #25030

[jelbourn]

LGTM

[crisbeto]

Changing the target to minor since there's a conflict with the patch branch.

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