Mention the FPS rate change and animation timer tick sync need

In case the user wants to modify the SAFE_TARGET_FPS rate (tooling parameter or project file option), the user should also consider updating the qsafeconstraints.h file and corresponding setting for the animation

static const quint32 ANIMATION_TIMER_TICK_IN_MS=20; //Animation timer in ms

The frames per second (FPS) setting is inverse to the timer tick, and they should match in order to get a smooth animation if the default FPS is not used.

Note: Maybe the constraints class documentation should also have some explicit mention to keep these values defined in different locations synced.

http://10.204.0.5/1.2/2020-10-13.00.01.01/SafetyManual/saferenderer-constraints.html#ANIMATION_TIMER_TICK_IN_MS-var