One phrase fix for idle_and_physics_processing.rst

Both, the _process() and _physics_process() are not called every time the engine draws a frame like its written here, only -process() does. _physics_process() gets called before each physics step like it's explained on this same page.

tutorials/scripting/idle_and_physics_processing.rst

@@ -54,7 +54,7 @@ possible to keep the physics interactions stable. You can change the interval
 between physics steps in the Project Settings, under Physics -> Common ->
 Physics Fps. By default, it's set to run 60 times per second.
 
-The engine calls this method every time it draws a frame:
+The engine calls this method before every physics step:
 
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  .. code-tab:: gdscript GDScript