Fix/deleteAnnotation

[SimonErm]

Currently the removeAnnotation method doesn't remove the specified annotation, because slice is used like splice for removal.

This PR adds a test for deleteAnnotation and fixes the behaviour by using slice in the correct way to delete an element of the array.

References:

• https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/splice
• https://stackoverflow.com/questions/11848534/remove-element-from-array-using-slice