Update dns-doctoring-has-been-disabled.md
Update dns-doctoring-has-been-disabled.md

Included Linux instructions.
mark-turpin/PublicKB,ack/PublicKB,keithresar/clc_public_kb,mfar78/PublicKB,heitortsergent/PublicKB,broneal/PublicKB,eschubert/PublicKB,jmalmadclc/PublicKB,nathanyoung/PublicKB,mclose/PublicKB,kjmd75/PublicKB,bburge/PublicKB,lmcornejo/PublicKB,SeanRobb/PublicKB,robertlesieur/PublicKB,csterwa/PublicKB,StephanieWong/PublicKB,BryGittyUp/PublicKB,daveshac/PublicKB,jwcolbert/PublicKB,robcaldwell/PublicKB,anthonyvetter/PublicKB,justinwithington/PublicKB,jruckle/PublicKB,jtowns3/PublicKB,thenley/PublicKB,adamd/PublicKB,leporaj/PublicKB,ian-plosker/PublicKB,maxim-clc/PublicKB,DLM1/PublicKB,BobStolzberg/PublicKB,appfog/PublicKB,jwebs1/PublicKB,duvander/PublicKB,ryanbrockman/PublicKB