Olá pessoal, fiz as seguintes alterações para funcionar na nova versão do JWT:
@Component
class JWTUtil(
    private val usuarioService: UsuarioService
) {
    @Value("\${jwt.secret}")
    private var secret: String = "2a12Dpr9yBjZksrrC34hnQEG1uDyF5HKckz3Cob4j5md1Jl3jXPF1ejzi"
    private val expiration: Long = 60000
    private val key = Keys.hmacShaKeyFor(secret.toByteArray(StandardCharsets.UTF_8))
    fun generateToken(username: String, authorities: MutableCollection<out GrantedAuthority>): String {
        return Jwts
            .builder()
            .subject(username)
            .claim("role", authorities)
            .expiration(Date(System.currentTimeMillis() + expiration))
            .signWith(key)
            .compact()
    }
    fun isValid(jwt: String?): Boolean {
        return try {
            Jwts.parser()
                .verifyWith(key)
                .build()
                .parseSignedClaims(jwt)
            true
        } catch (e: IllegalArgumentException) {
            false
        }
    }
    fun getAuthentication(jwt: String?): UsernamePasswordAuthenticationToken {
        val username = Jwts.parser()
            .verifyWith(key)
            .build()
            .parseSignedClaims(jwt)
            .payload
            .subject
        val user = usuarioService.loadUserByUsername(username.toString())
        return UsernamePasswordAuthenticationToken(username, null, user.authorities)
    }
}
Aqui funcionou perfeitamente.
 
             
            