Documentation is wrong about immutability

[DarioViva42]

jjwt/api/src/main/java/io/jsonwebtoken/lang/Collections.java

Line 94 in 5812f63

public static <T> Set<T> asSet(Collection<T> c) {

You tell users, that asSet returns an immutable Set.

@return a type-safe immutable {@code Set} containing the specified collection elements.

This is not true, when you pass in a mutable Set. In this case the Collection is only cast to a Set. You probably want to change the documentation or use java.util.Collections.unmodifiableSet