Hello:
In the properties of the repeating section to the right of the text area that holds the sections that can be inserted, there is a Modify button. Highlight the section and select Modify. In the Section Properties window that opens, select the Customize Commands button. Change the dropdown by Action to Remove and deselect any selected checkboxes. Then, when you preview your form, you'll see the remove options are no longer on the menu for the repeating section. This will not, however, prevent a user from being able to use the Cut command on the right click menu for a section -- I do not know of a way to disable that.