Convert a series expansion into a polynomial : convert convertir

### 2.24.22 Convert a series expansion into a polynomial : `convert convertir`

`convert`, with the option `polynom`, converts a Taylor series into a polynomial. It should be used for operations like drawing the graph of the Taylor series of a function near a point.
`convert` takes two arguments : an expression and the option `polynom`.
`convert` replaces the `order_size` functions by 0 inside the expression.
Input :

`convert(taylor(sin(x)),polynom)`

Output :

`x+1/-6*x```^```3+1/120*```x^```5+x```^```6*0`

Input :

`convert(series(sin(x),x=0,6),polynom)`

Output :

`x+1/-6*x```^```3+1/120*```x^```5+x```^```7*0`