Fix a minor grammatical error in forth.md
Fix a minor grammatical error in forth.md
rpottsoh/x-common,Vankog/problem-specifications,ErikSchierboom/x-common,exercism/x-common,kgengler/x-common,exercism/x-common,jmluy/x-common,ErikSchierboom/x-common,Vankog/problem-specifications,wobh/x-common,kgengler/x-common,jmluy/x-common,rpottsoh/x-common,jmluy/x-common,petertseng/x-common,petertseng/x-common