You can use the replace code \rep to remove the verse text from verse 1 so you are left with just the heading text. You need to use \refnp to not bring in the paragraph marker, so you will need to provide the heading marker \s1 for the heading text:
\inc s
\s1
\refnp GEN 6:1
\rep When human beings began to increase in number on the earth and daughters were born to them,=>
\ref GEN 6:5-6
Notice the \rep statement ends with =>, which means replace with nothing, or delete. This will give you:
\s1 Wickedness in the World
\p \v 5 The \nd Lord\nd* saw how great the wickedness of the human race had become on the earth, and that every inclination of the thoughts of the human heart was only evil all the time. \v 6 The \nd Lord\nd* regretted that he had made human beings on the earth, and his heart was deeply troubled.