아래 코드를 추가해주면 됩니다.
builder.Services.AddSwaggerGen(c =>
{
    c.AddSecurityDefinition("Bearer", new OpenApiSecurityScheme()
    {
        Name = "Authorization",
        Type = SecuritySchemeType.ApiKey,
        Scheme = "Bearer",
        BearerFormat = "JWT",
        In = ParameterLocation.Header,
        Description = "JWT Authorization header using the Bearer scheme."
    });
    c.AddSecurityRequirement(new OpenApiSecurityRequirement
    {
        {
            new OpenApiSecurityScheme
            {
                Reference = new OpenApiReference
                {
                    Type = ReferenceType.SecurityScheme,
                    Id = "Bearer"
                }
            },
            Array.Empty<string>()
        }
    });
});