Replace division slash with fraction slash on Neo2 (de) layout

The definition of German keyboard layout Neo2 (or just Neo) differs from the official layout reference file of the project in one position (see line 348): the character for KP_Divide on „Ebene4“ (which is xkb layer 5) should be a Fraction Slash (U+2044), whereas the definition in xkb yet defines a Division Slash (U+2215).

Due to several circumstances, the wrong character was sent upstream to xkeyboard-config in March 2010, and until recently, no one detected the difference. We, the Neo maintainers and users, then had a discussion in our issue tracker (unfortunately all in German) about why there is a mismatch and what should be the correct character. We agreed upon that the Neo reference is representative and the fraction slash is considered to be of more use.

I already compared the rest of both definitions: no further differences found. All Neo-based layouts like AdNW or Bone will inherit this change, which is fine because they share the numpad definition.