Fix client tests list

[3Rafal]

When trying to run tests according to readme (dotnet run -- RunTestsHeadless), I got hit with:

./Client.Tests.fs(33,9): (33,28) error FSHARP: This value is not a function and cannot be applied. (code 3) Compilation failed

The problem is that there is no separator, so instead of two-element list we have invalid function application. After adding separator tests run correctly.

Similar logic but without directive can be found in Server.Tests.fs file:

let all = testList "All" [ Shared.Tests.shared; server ]