update docs

Author: akwasniewski

packages/docs-gesture-handler/docs/fundamentals/state-manager.mdx

@@ -68,7 +68,7 @@ const styles = StyleSheet.create({
 
 ### Outside gesture definition
 
-If you want to control gesture lifecycle outside of it, you can use `handlerTag` from created gesture object.
+If you want to control gesture lifecycle outside of it, you can use `handlerTag` from created gesture object. Note that gestures can only be activated after it has begun, that is, after it has received received touch events.
 
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@@ -179,14 +179,6 @@ const styles = {
 
 `GestureStateManager` provides methods to manipulate gesture's state imperatively.
 
-### begin
-
-```tsx
-begin: (handlerTag: number) => void;
-```
-
-Triggers [`onBegin`](/docs/fundamentals/callbacks-events#onbegin) callback on gesture with specified `handlerTag`.
-
 ### activate
 
 ```tsx