Remove isMultiset from IBLTMultiset constructor docs

[novakboskov]

What was the idea of isMultiset parameter in IBLTMultiset constructor? It is not used in the constructor.

    /**
     * Constructs an IBLT object with size relative to expectedNumEntries.
     * @param expectedNumEntries The expected amount of entries to be placed into the IBLT
     * @param _valueSize The size of the values being added, in bits
     * @param isMultiset Is the IBLT going to store multiset values, default is false
     */
    IBLTMultiset(size_t expectedNumEntries, size_t _valueSize);

[arorashu]

Fixed in PR#78