Blueprint Function Library variables can be promoted out of scope

Input parameters can be promoted to variables from the context menu when dropped on an empty graph. Per [Link Removed] this is not expected and dangerous for users to use.

This is reproducible as far back as //UE4/Release-4.22 cl 8065115 so this is not a regression.

1. Open any project
2. Create a new Blueprint Function Libary (BFL)
   • Right click content browser > Blueprints > Blueprint Function Libarary
3. Open the new BFL
4. Create a new function
5. Create a new input variable for that function
6. Drag off the input pin and release the mouse on a the empty graph
7. Select 'Promote to Variable' from the context menu

Result
The input parameter is promoted to a global variable and the BFL can no longer succesfully compile

Expected
Only local variables should be declared within BFLs