docs: fix(getting-started): replace structlog to polyfactory for Polyfactory section (#4385)

Author: Peopl3s

docs/getting-started.rst

@@ -57,7 +57,7 @@ Installation
         :code:`pip install litestar[mako]`
 
     :ref:`Polyfactory to generate OpenAPI examples <usage/openapi/schema_generation:Generating examples>`
-        :code:`pip install litestar[structlog]`
+        :code:`pip install litestar[polyfactory]`
 
     :doc:`HTMX plugin </usage/htmx>`
         :code:`pip install litestar[htmx]`