Fix number of additional overloads on lambda parameter's member recommendations

[jhinder]

Fixes #61343.

The lambda parameter's type was added to the array twice, causing its members to be considered twice too. This resulted in the wrong number of additional overloads being shown in the completion item's tooltip ($2n-1$ instead of $n-1$).
This fix makes the addition of the type symbol conditional so that it doesn't appear more than once in the array of type symbols.

[genlu]

Thanks!