Fixed "theme" naming error
Fixed "theme" naming error

The Category field guidance incorrectly referred to the metadata name as "category" when it should be "theme."
bpushed/project-open-data.github.io,portofsandiego/project-open-data.github.io,fedspendingtransparency/fedspendingtransparency.github.io,fedspendingtransparency/fedspendingtransparency.github.io,pjdufour/project-open-data.github.io,bpushed/project-open-data.github.io,pjdufour/project-open-data.github.io,Chuck8080/opendata,cmurphyUSAID/implementation-guide,fedspendingtransparency/fedspendingtransparency.github.io,fedspendingtransparency/fedspendingtransparency.github.io,pjdufour/project-open-data.github.io,portofsandiego/project-open-data.github.io,pjdufour/project-open-data.github.io,Chuck8080/opendata,portofsandiego/project-open-data.github.io,judecalvillo/project-open-data.github.io,portofsandiego/project-open-data.github.io,judecalvillo/project-open-data.github.io