Update documentation in waxman_graph.
Update documentation in waxman_graph.

The waxman graph documentation was incorrectly documented.
Changed the positive exponential to a negative exponential
yashu-seth/networkx,jakevdp/networkx,JamesClough/networkx,NvanAdrichem/networkx,cmtm/networkx,jtorrents/networkx,dmoliveira/networkx,harlowja/networkx,Sixshaman/networkx,aureooms/networkx,jakevdp/networkx,kernc/networkx,bzero/networkx,sharifulgeo/networkx,farhaanbukhsh/networkx,ionanrozenfeld/networkx,michaelpacer/networkx,kai5263499/networkx,chrisnatali/networkx,jni/networkx,nathania/networkx,nathania/networkx,blublud/networkx,nathania/networkx,jtorrents/networkx,farhaanbukhsh/networkx,jfinkels/networkx,harlowja/networkx,sharifulgeo/networkx,RMKD/networkx,kai5263499/networkx,ionanrozenfeld/networkx,dhimmel/networkx,ghdk/networkx,jni/networkx,debsankha/networkx,dhimmel/networkx,debsankha/networkx,debsankha/networkx,jni/networkx,kernc/networkx,kernc/networkx,dhimmel/networkx,blublud/networkx,dmoliveira/networkx,tmilicic/networkx,chrisnatali/networkx,farhaanbukhsh/networkx,kai5263499/networkx,sharifulgeo/networkx,SanketDG/networkx,chrisnatali/networkx,bzero/networkx,ltiao/networkx,ghdk/networkx,OrkoHunter/networkx,RMKD/networkx,ionanrozenfeld/networkx,beni55/networkx,ghdk/networkx,wasade/networkx,bzero/networkx,RMKD/networkx,jcurbelo/networkx,dmoliveira/networkx,goulu/networkx,harlowja/networkx,jakevdp/networkx,aureooms/networkx,andnovar/networkx,blublud/networkx,aureooms/networkx