Refactor: Remove redundant else in get_activation

[leaderofARS]

Hi! I was reading through
activations.py
to better understand how the library handles activation mappings, and I noticed a small opportunity to clean up the
get_activation
function.

Since the if block returns early, the else block isn't actually needed. I've removed it to flatten the logic a bit. I know it's a tiny change, but I figured it was worth polishing up to keep the code readable.

[Rocketknight1]

Hey! Can you run pip install -e .[quality] followed by make style to get the code quality tests to pass?