fix: Drop generated requires-python upper bounds for uv and PDM

[johnthagen]

requires-python has a long and sorted history in the Python community

• https://docs.astral.sh/uv/concepts/resolution/#universal-resolution

When evaluating requires-python ranges for dependencies, uv only considers lower bounds and ignores upper bounds entirely. For example, >=3.8, <4 is treated as >=3.8

Remove the upper bound on generated clients to avoid pushing users into this without need.

[dbanty]

Thanks!