fix: resolve race condition in ThrottleController.Update method

[forkfury]

Fix race condition in ThrottleController.Update by changing RLock to Lock

The Update method was using RLock to read strategy reference, then calling
strategy.Update() without holding the lock. This created a race condition
where SetStrategy could change the strategy between reading the reference
and using it, leading to inconsistent throttling behavior.

Using Lock instead of RLock ensures the entire Update operation is atomic,
preventing SetStrategy from modifying the strategy while Update executes.
This guarantees thread safety when controller type is changed at runtime.