Simplify embedded field access in generated mock constructors

In the generated mock constructors, the code currently uses mock.Mock.Test(t) to register the testing interface:

func NewMyMock(t interface {
    mock.TestingT
    Cleanup(func())
}) *MyMock {
    mock := &MyMock{}
    mock.Mock.Test(t)
    t.Cleanup(func() { mock.AssertExpectations(t) })
    return mock
}

Since Mock is an embedded field in the generated struct, Go promotes its methods automatically. The explicit mock.Mock.Test(t) is redundant and can be simplified to mock.Test(t):

mock.Test(t)

This is a minor cleanup but aligns with Go idiomatic usage of embedded types, where accessing promoted methods directly is the standard practice.