Replace <label> with #label invocation
This commit refactors our View layer’s notes#new template by replacing
a hard-coded <label> element with a call to
ActionView::Helpers::FormBuilder#label.
By passing :content as the first argument, the generated <label>
element’s for attribute will declare for="content", which
correspond to the <textarea> element’s id="content" and ensures that
the label corresponds to the form’s field.
When we run the test again, it is still passing.