[#55033] added distance to github tab header

[Kharonus]

#55033

WAT?

• used same distance, that button in relations tab has

Additional information

Especially looking at @HDinger, please tell me, if the solution is too easy and if we should put more effort in redesigning this header. I checked other tabs with buttons, found the relations tab. There the button itself has a margin bottom of 4px, forcing the grid cell to have this distance.