Change preview4 references to RC4
Change preview4 references to RC4

Preview4 is actually RC4 as all documentation and dotnet --info shows. I thought they were 2 separate things.
livarcocc/cli-1,harshjain2/cli,harshjain2/cli,mlorbetske/cli,jonsequitur/cli,mlorbetske/cli,EdwardBlair/cli,nguerrera/cli,blackdwarf/cli,blackdwarf/cli,nguerrera/cli,blackdwarf/cli,dasMulli/cli,nguerrera/cli,ravimeda/cli,blackdwarf/cli,johnbeisner/cli,mlorbetske/cli,svick/cli,EdwardBlair/cli,Faizan2304/cli,mlorbetske/cli,jonsequitur/cli,johnbeisner/cli,svick/cli,livarcocc/cli-1,dasMulli/cli,jonsequitur/cli,svick/cli,ravimeda/cli,dasMulli/cli,livarcocc/cli-1,Faizan2304/cli,Faizan2304/cli,ravimeda/cli,harshjain2/cli,EdwardBlair/cli,johnbeisner/cli,jonsequitur/cli,nguerrera/cli