Ok I don't know how but one of my form is stuck in Visual Studio common items and I don't know how to remove it.
All I did is copy the original form say form-x and pasted it in solution explorer.
This screenshot shows the issue:
And now I have no idea how to remove it?
According to Create item templates, find the item template location and delete it.
%USERPROFILE%\Documents\Visual Studio <version>\My Exported Templates.